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SEC Schedule, Article 12-28, Real Estate and Accumulated Depreciation (Details) - USD ($) | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances | [1] | $ 4,166,379,000 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 5,637,035,000 |  |  |  |
Original Building |  | 15,478,086,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 6,306,350,000 |  |  |  |
Land and Improvements | [2] | 5,953,798,000 |  |  |  |
Building and Improvements | [3] | 20,223,332,000 |  |  |  |
Land held for development | [5] | 697,061,000 | [4] | $ 721,501,000 |  |
Development and Construction in Progress |  | 547,280,000 |  | 406,574,000 |  |
Total |  | 27,421,471,000 |  | 25,744,214,000 | $ 24,108,220,000 | $ 23,303,303,000
Accumulated Depreciation |  | 6,841,404,000 |  | 6,260,992,000 | 5,848,183,000 | 5,501,637,000
Furniture, Fixtures and Equipment |  | 53,716,000 |  | 50,310,000 |  |
Aggregate cost for tax purpose |  | 25,200,000,000 |  |  |  |
Real Estate Aggregate Accumulated Depreciation For Tax Purposes |  | 5,900,000,000 |  |  |  |
Debt Issuance Costs, Net |  | (33,600,000) |  |  |  |
Right-of-use assets - finance leases |  | 401,680,000 | [6] | 237,510,000 |  |
Operating Lease, Right-of-Use Asset | [6] | $ 324,298,000 |  | 167,351,000 |  |
Maximum [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Real Estate and Accumulated Depreciation, Life Used for Depreciation |  | 40 years |  |  |  |
Furniture, fixtures, and equipment |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Accumulated Depreciation Related to Furniture, Fixtures and Equipment |  | $ 40,324,000 |  |  |  |
Land and Land Improvements [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Right-of-use assets - finance leases |  | 378,276,000 |  |  |  |
Operating Lease, Right-of-Use Asset |  | 324,298,000 |  |  |  |
Buildings and improvements |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Right-of-use assets - finance leases |  | 23,404,000 |  |  |  |
767Fifth Avenue (the General Motors Building) | Office and Life Sciences Building [Member] |  |  |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances |  | 2,288,004,000 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 1,796,252,000 |  |  |  |
Original Building |  | 1,532,654,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 365,829,000 |  |  |  |
Land and Improvements |  | 1,796,252,000 |  |  |  |
Building and Improvements |  | 1,898,483,000 |  |  |  |
Total |  | 3,694,735,000 |  |  |  |
Accumulated Depreciation |  | $ 507,660,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Prudential Center | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 92,077,000 |  |  |  |
Original Building |  | 948,357,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 791,280,000 |  |  |  |
Land and Improvements |  | 115,634,000 |  |  |  |
Building and Improvements |  | 1,687,021,000 |  |  |  |
Development and Construction in Progress |  | 29,059,000 |  |  |  |
Total |  | 1,831,714,000 |  |  |  |
Accumulated Depreciation |  | $ 774,225,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Embarcadero Center | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 179,697,000 |  |  |  |
Original Building |  | 847,410,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 524,483,000 |  |  |  |
Land and Improvements |  | 195,986,000 |  |  |  |
Building and Improvements |  | 1,355,604,000 |  |  |  |
Total |  | 1,551,590,000 |  |  |  |
Accumulated Depreciation |  | $ 781,405,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
399 Park Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 339,200,000 |  |  |  |
Original Building |  | 700,358,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 408,846,000 |  |  |  |
Land and Improvements |  | 354,107,000 |  |  |  |
Building and Improvements |  | 1,094,297,000 |  |  |  |
Total |  | 1,448,404,000 |  |  |  |
Accumulated Depreciation |  | $ 482,752,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
601 Lexington Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances |  | $ 989,181,000 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 241,600,000 |  |  |  |
Original Building |  | 494,782,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 545,612,000 |  |  |  |
Land and Improvements |  | 289,639,000 |  |  |  |
Building and Improvements |  | 992,355,000 |  |  |  |
Total |  | 1,281,994,000 |  |  |  |
Accumulated Depreciation |  | $ 372,795,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Salesforce Tower | Office and Life Sciences Building [Member] |  |  |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances |  | $ 0 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 200,349,000 |  |  |  |
Original Building |  | 946,205,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 7,623,000 |  |  |  |
Land and Improvements |  | 200,349,000 |  |  |  |
Building and Improvements |  | 953,828,000 |  |  |  |
Total |  | 1,154,177,000 |  |  |  |
Accumulated Depreciation |  | $ 159,274,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
200 Clarendon Street and Garage | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 219,543,000 |  |  |  |
Original Building |  | 667,884,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 251,372,000 |  |  |  |
Land and Improvements |  | 250,910,000 |  |  |  |
Building and Improvements |  | 887,889,000 |  |  |  |
Total |  | 1,138,799,000 |  |  |  |
Accumulated Depreciation |  | $ 338,529,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
250 West 55th Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 285,263,000 |  |  |  |
Original Building |  | 603,167,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 52,917,000 |  |  |  |
Land and Improvements |  | 285,263,000 |  |  |  |
Building and Improvements |  | 656,084,000 |  |  |  |
Total |  | 941,347,000 |  |  |  |
Accumulated Depreciation |  | $ 198,081,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
100 Federal Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 131,067,000 |  |  |  |
Original Building |  | 435,954,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 127,199,000 |  |  |  |
Land and Improvements |  | 131,067,000 |  |  |  |
Building and Improvements |  | 563,153,000 |  |  |  |
Total |  | 694,220,000 |  |  |  |
Accumulated Depreciation |  | $ 172,079,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Times Square Tower | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 165,413,000 |  |  |  |
Original Building |  | 380,438,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 140,281,000 |  |  |  |
Land and Improvements |  | 169,193,000 |  |  |  |
Building and Improvements |  | 516,939,000 |  |  |  |
Total |  | 686,132,000 |  |  |  |
Accumulated Depreciation |  | $ 256,942,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Madison Centre | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 104,641,000 |  |  |  |
Original Building |  | 564,336,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 4,082,000 |  |  |  |
Land and Improvements |  | 104,641,000 |  |  |  |
Building and Improvements |  | 568,418,000 |  |  |  |
Total |  | 673,059,000 |  |  |  |
Accumulated Depreciation |  | $ 35,516,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Carnegie Center | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 142,666,000 |  |  |  |
Original Building |  | 316,856,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 177,545,000 |  |  |  |
Land and Improvements |  | 94,243,000 |  |  |  |
Building and Improvements |  | 484,024,000 |  |  |  |
Land held for development |  | 58,800,000 |  |  |  |
Total |  | 637,067,000 |  |  |  |
Accumulated Depreciation |  | $ 267,232,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Santa Monica Business Park [Member] | Office and Life Sciences Building [Member] |  |  |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances |  | $ 295,649,000 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 46,360,000 |  |  |  |
Original Building |  | 410,421,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 164,229,000 |  |  |  |
Land and Improvements |  | 210,471,000 |  |  |  |
Building and Improvements |  | 410,535,000 |  |  |  |
Land held for development |  | 4,000 |  |  |  |
Total |  | 621,010,000 |  |  |  |
Accumulated Depreciation |  | $ 865,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Reston Next | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 35,549,000 |  |  |  |
Original Building |  | 525,277,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 0 |  |  |  |
Land and Improvements |  | 2,901,000 |  |  |  |
Building and Improvements |  | 557,925,000 |  |  |  |
Total |  | 560,826,000 |  |  |  |
Accumulated Depreciation |  | $ 32,504,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
125 Broadway | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 126,364,000 |  |  |  |
Original Building |  | 433,662,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 4,000,000 |  |  |  |
Land and Improvements |  | 126,364,000 |  |  |  |
Building and Improvements |  | 437,662,000 |  |  |  |
Total |  | 564,026,000 |  |  |  |
Accumulated Depreciation |  | $ 20,717,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Atlantic Wharf | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 63,988,000 |  |  |  |
Original Building |  | 454,537,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 39,399,000 |  |  |  |
Land and Improvements |  | 63,988,000 |  |  |  |
Building and Improvements |  | 493,936,000 |  |  |  |
Total |  | 557,924,000 |  |  |  |
Accumulated Depreciation |  | $ 180,686,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
2100 Pennsylvania Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 185,203,000 |  |  |  |
Original Building |  | 324,206,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 0 |  |  |  |
Land and Improvements |  | 185,203,000 |  |  |  |
Building and Improvements |  | 324,206,000 |  |  |  |
Total |  | 509,409,000 |  |  |  |
Accumulated Depreciation |  | $ 20,768,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
599 Lexington Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 81,040,000 |  |  |  |
Original Building |  | 100,507,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 258,659,000 |  |  |  |
Land and Improvements |  | 87,852,000 |  |  |  |
Building and Improvements |  | 352,354,000 |  |  |  |
Total |  | 440,206,000 |  |  |  |
Accumulated Depreciation |  | $ 197,429,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Fountain Square | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 56,853,000 |  |  |  |
Original Building |  | 306,298,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 49,874,000 |  |  |  |
Land and Improvements |  | 56,853,000 |  |  |  |
Building and Improvements |  | 356,172,000 |  |  |  |
Total |  | 413,025,000 |  |  |  |
Accumulated Depreciation |  | $ 111,481,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
510 Madison Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 103,000,000 |  |  |  |
Original Building |  | 253,665,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 33,100,000 |  |  |  |
Land and Improvements |  | 103,000,000 |  |  |  |
Building and Improvements |  | 286,765,000 |  |  |  |
Total |  | 389,765,000 |  |  |  |
Accumulated Depreciation |  | $ 104,052,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
325 Main Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances | [8] | $ 0 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 21,596,000 |  |  |  |
Original Building |  | 312,492,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 30,933,000 |  |  |  |
Land and Improvements |  | 21,596,000 |  |  |  |
Building and Improvements |  | 343,425,000 |  |  |  |
Total |  | 365,021,000 |  |  |  |
Accumulated Depreciation |  | $ 14,833,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
680 Folsom Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 72,545,000 |  |  |  |
Original Building |  | 219,766,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 8,026,000 |  |  |  |
Land and Improvements |  | 72,545,000 |  |  |  |
Building and Improvements |  | 227,792,000 |  |  |  |
Total |  | 300,337,000 |  |  |  |
Accumulated Depreciation |  | $ 80,964,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
145 Broadway | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 121,000 |  |  |  |
Original Building |  | 273,013,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 26,359,000 |  |  |  |
Land and Improvements |  | 23,367,000 |  |  |  |
Building and Improvements |  | 276,126,000 |  |  |  |
Total |  | 299,493,000 |  |  |  |
Accumulated Depreciation |  | $ 35,390,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
2200 Pennsylvania Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 183,541,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 114,090,000 |  |  |  |
Land and Improvements |  | 102,979,000 |  |  |  |
Building and Improvements |  | 194,652,000 |  |  |  |
Total |  | 297,631,000 |  |  |  |
Accumulated Depreciation |  | $ 77,357,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
South of Market and Democracy Tower | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 13,603,000 |  |  |  |
Original Building |  | 237,479,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 30,952,000 |  |  |  |
Land and Improvements |  | 13,687,000 |  |  |  |
Building and Improvements |  | 268,347,000 |  |  |  |
Total |  | 282,034,000 |  |  |  |
Accumulated Depreciation |  | $ 108,973,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Bay Colony Corporate Center | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 18,789,000 |  |  |  |
Original Building |  | 148,451,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 96,639,000 |  |  |  |
Land and Improvements |  | 18,789,000 |  |  |  |
Building and Improvements |  | 240,416,000 |  |  |  |
Land held for development |  | 4,674,000 |  |  |  |
Total |  | 263,879,000 |  |  |  |
Accumulated Depreciation |  | $ 113,123,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
535 Mission Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 40,933,000 |  |  |  |
Original Building |  | 148,378,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 4,629,000 |  |  |  |
Land and Improvements |  | 40,934,000 |  |  |  |
Building and Improvements |  | 153,006,000 |  |  |  |
Total |  | 193,940,000 |  |  |  |
Accumulated Depreciation |  | $ 46,615,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Mountain View Research Park | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 95,066,000 |  |  |  |
Original Building |  | 68,373,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 21,069,000 |  |  |  |
Land and Improvements |  | 95,066,000 |  |  |  |
Building and Improvements |  | 89,442,000 |  |  |  |
Total |  | 184,508,000 |  |  |  |
Accumulated Depreciation |  | $ 33,095,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Reservoir Place | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 18,605,000 |  |  |  |
Original Building |  | 104,124,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 56,160,000 |  |  |  |
Land and Improvements |  | 20,108,000 |  |  |  |
Building and Improvements |  | 156,954,000 |  |  |  |
Land held for development |  | 1,827,000 |  |  |  |
Total |  | 178,889,000 |  |  |  |
Accumulated Depreciation |  | $ 90,808,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
140 Kendrick Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 18,095,000 |  |  |  |
Original Building |  | 66,905,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 71,861,000 |  |  |  |
Land and Improvements |  | 19,092,000 |  |  |  |
Building and Improvements |  | 137,769,000 |  |  |  |
Total |  | 156,861,000 |  |  |  |
Accumulated Depreciation |  | $ 46,586,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
1330 Connecticut Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 25,982,000 |  |  |  |
Original Building |  | 82,311,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 39,924,000 |  |  |  |
Land and Improvements |  | 27,135,000 |  |  |  |
Building and Improvements |  | 121,082,000 |  |  |  |
Total |  | 148,217,000 |  |  |  |
Accumulated Depreciation |  | $ 53,332,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
880 Winter Street [Member] | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 15,597,000 |  |  |  |
Original Building |  | 37,255,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 95,265,000 |  |  |  |
Land and Improvements |  | 15,597,000 |  |  |  |
Building and Improvements |  | 132,520,000 |  |  |  |
Total |  | 148,117,000 |  |  |  |
Accumulated Depreciation |  | $ 10,056,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
One Freedom Square | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 9,929,000 |  |  |  |
Original Building |  | 84,504,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 48,985,000 |  |  |  |
Land and Improvements |  | 11,293,000 |  |  |  |
Building and Improvements |  | 132,125,000 |  |  |  |
Total |  | 143,418,000 |  |  |  |
Accumulated Depreciation |  | $ 68,406,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Two Freedom Square | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 13,930,000 |  |  |  |
Original Building |  | 77,739,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 45,068,000 |  |  |  |
Land and Improvements |  | 15,420,000 |  |  |  |
Building and Improvements |  | 121,317,000 |  |  |  |
Total |  | 136,737,000 |  |  |  |
Accumulated Depreciation |  | $ 44,662,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Kingstowne Towne Center | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 18,021,000 |  |  |  |
Original Building |  | 109,038,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 4,665,000 |  |  |  |
Land and Improvements |  | 18,062,000 |  |  |  |
Building and Improvements |  | 113,662,000 |  |  |  |
Total |  | 131,724,000 |  |  |  |
Accumulated Depreciation |  | $ 54,480,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
One and Two Reston Overlook | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 16,456,000 |  |  |  |
Original Building |  | 66,192,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 45,224,000 |  |  |  |
Land and Improvements |  | 16,179,000 |  |  |  |
Building and Improvements |  | 111,693,000 |  |  |  |
Total |  | 127,872,000 |  |  |  |
Accumulated Depreciation |  | $ 61,572,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Shady Grove Innovation District [Member] | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 52,030,000 |  |  |  |
Original Building |  | 64,212,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 10,676,000 |  |  |  |
Land and Improvements |  | 26,834,000 |  |  |  |
Building and Improvements |  | 34,954,000 |  |  |  |
Land held for development |  | 65,130,000 |  |  |  |
Total |  | 126,918,000 |  |  |  |
Accumulated Depreciation |  | $ 4,701,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Weston Corporate Center | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 25,753,000 |  |  |  |
Original Building |  | 92,312,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,038,000 |  |  |  |
Land and Improvements |  | 25,854,000 |  |  |  |
Building and Improvements |  | 93,249,000 |  |  |  |
Total |  | 119,103,000 |  |  |  |
Accumulated Depreciation |  | $ 41,485,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
355 Main Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances |  | $ 593,545,000 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 18,863,000 |  |  |  |
Original Building |  | 53,346,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 41,772,000 |  |  |  |
Land and Improvements |  | 21,173,000 |  |  |  |
Building and Improvements |  | 92,808,000 |  |  |  |
Total |  | 113,981,000 |  |  |  |
Accumulated Depreciation |  | $ 36,957,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
17Fifty Presidents Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 113,362,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 162,000 |  |  |  |
Land and Improvements |  | 0 |  |  |  |
Building and Improvements |  | 113,524,000 |  |  |  |
Total |  | 113,524,000 |  |  |  |
Accumulated Depreciation |  | $ 16,624,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
200 West Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 16,148,000 |  |  |  |
Original Building |  | 24,983,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 71,199,000 |  |  |  |
Land and Improvements |  | 16,813,000 |  |  |  |
Building and Improvements |  | 95,160,000 |  |  |  |
Land held for development |  | 357,000 |  |  |  |
Total |  | 112,330,000 |  |  |  |
Accumulated Depreciation |  | $ 28,192,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Discovery Square | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 11,198,000 |  |  |  |
Original Building |  | 71,782,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 21,744,000 |  |  |  |
Land and Improvements |  | 12,533,000 |  |  |  |
Building and Improvements |  | 92,191,000 |  |  |  |
Total |  | 104,724,000 |  |  |  |
Accumulated Depreciation |  | $ 57,015,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
10 CityPoint | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 1,953,000 |  |  |  |
Original Building |  | 85,752,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 7,571,000 |  |  |  |
Land and Improvements |  | 2,288,000 |  |  |  |
Building and Improvements |  | 92,988,000 |  |  |  |
Total |  | 95,276,000 |  |  |  |
Accumulated Depreciation |  | $ 24,003,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
90 Broadway | Office and Life Sciences Building [Member] |  |  |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances | [8] | $ 0 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 19,104,000 |  |  |  |
Original Building |  | 52,078,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 22,742,000 |  |  |  |
Land and Improvements |  | 20,785,000 |  |  |  |
Building and Improvements |  | 73,139,000 |  |  |  |
Total |  | 93,924,000 |  |  |  |
Accumulated Depreciation |  | $ 31,538,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Waltham Weston Corporate Center | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 10,385,000 |  |  |  |
Original Building |  | 60,694,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 20,705,000 |  |  |  |
Land and Improvements |  | 11,097,000 |  |  |  |
Building and Improvements |  | 80,687,000 |  |  |  |
Total |  | 91,784,000 |  |  |  |
Accumulated Depreciation |  | $ 45,601,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
153 & 211 Second Avenue [Member] | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 33,233,000 |  |  |  |
Original Building |  | 55,940,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 718,000 |  |  |  |
Land and Improvements |  | 33,233,000 |  |  |  |
Building and Improvements |  | 55,940,000 |  |  |  |
Land held for development |  | 718,000 |  |  |  |
Total |  | 89,891,000 |  |  |  |
Accumulated Depreciation |  | $ 6,186,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
230 CityPoint | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 13,189,000 |  |  |  |
Original Building |  | 49,823,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 24,297,000 |  |  |  |
Land and Improvements |  | 13,807,000 |  |  |  |
Building and Improvements |  | 73,502,000 |  |  |  |
Total |  | 87,309,000 |  |  |  |
Accumulated Depreciation |  | $ 40,959,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
20 Citypoint | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 4,887,000 |  |  |  |
Original Building |  | 72,764,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 7,072,000 |  |  |  |
Land and Improvements |  | 4,887,000 |  |  |  |
Building and Improvements |  | 79,836,000 |  |  |  |
Total |  | 84,723,000 |  |  |  |
Accumulated Depreciation |  | $ 13,031,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Sumner Square | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 624,000 |  |  |  |
Original Building |  | 28,745,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 51,253,000 |  |  |  |
Land and Improvements |  | 27,837,000 |  |  |  |
Building and Improvements |  | 52,785,000 |  |  |  |
Total |  | 80,622,000 |  |  |  |
Accumulated Depreciation |  | $ 32,911,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
77 CityPoint | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 13,847,000 |  |  |  |
Original Building |  | 60,383,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,506,000 |  |  |  |
Land and Improvements |  | 14,023,000 |  |  |  |
Building and Improvements |  | 61,713,000 |  |  |  |
Total |  | 75,736,000 |  |  |  |
Accumulated Depreciation |  | $ 26,943,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
2440 West El Camino Real | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 16,741,000 |  |  |  |
Original Building |  | 51,285,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 6,565,000 |  |  |  |
Land and Improvements |  | 16,741,000 |  |  |  |
Building and Improvements |  | 57,850,000 |  |  |  |
Total |  | 74,591,000 |  |  |  |
Accumulated Depreciation |  | $ 21,469,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Wisconsin Place | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 53,349,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 13,834,000 |  |  |  |
Land and Improvements |  | 0 |  |  |  |
Building and Improvements |  | 67,183,000 |  |  |  |
Total |  | 67,183,000 |  |  |  |
Accumulated Depreciation |  | $ 28,960,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Reston Corporate Center | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 9,135,000 |  |  |  |
Original Building |  | 50,857,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 4,489,000 |  |  |  |
Land and Improvements |  | 10,148,000 |  |  |  |
Building and Improvements |  | 54,333,000 |  |  |  |
Total |  | 64,481,000 |  |  |  |
Accumulated Depreciation |  | $ 34,194,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
255 Main Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 134,000 |  |  |  |
Original Building |  | 25,110,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 33,330,000 |  |  |  |
Land and Improvements |  | 548,000 |  |  |  |
Building and Improvements |  | 58,026,000 |  |  |  |
Total |  | 58,574,000 |  |  |  |
Accumulated Depreciation |  | $ 43,927,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
University Place | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 37,091,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 15,768,000 |  |  |  |
Land and Improvements |  | 4,807,000 |  |  |  |
Building and Improvements |  | 48,052,000 |  |  |  |
Total |  | 52,859,000 |  |  |  |
Accumulated Depreciation |  | $ 37,130,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
890 Winter Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 13,913,000 |  |  |  |
Original Building |  | 28,557,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 8,507,000 |  |  |  |
Land and Improvements |  | 13,913,000 |  |  |  |
Building and Improvements |  | 37,064,000 |  |  |  |
Total |  | 50,977,000 |  |  |  |
Accumulated Depreciation |  | $ 7,296,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Capital Gallery | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 4,725,000 |  |  |  |
Original Building |  | 29,565,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 10,361,000 |  |  |  |
Land and Improvements |  | 8,662,000 |  |  |  |
Building and Improvements |  | 35,989,000 |  |  |  |
Total |  | 44,651,000 |  |  |  |
Accumulated Depreciation |  | $ 23,764,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
North First Business Park | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 23,398,000 |  |  |  |
Original Building |  | 13,069,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 5,258,000 |  |  |  |
Land and Improvements |  | 23,378,000 |  |  |  |
Building and Improvements |  | 18,347,000 |  |  |  |
Total |  | 41,725,000 |  |  |  |
Accumulated Depreciation |  | $ 17,354,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
150 Broadway | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 850,000 |  |  |  |
Original Building |  | 25,042,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 15,749,000 |  |  |  |
Land and Improvements |  | 1,323,000 |  |  |  |
Building and Improvements |  | 40,318,000 |  |  |  |
Total |  | 41,641,000 |  |  |  |
Accumulated Depreciation |  | $ 18,506,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
105 Broadway | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 1,299,000 |  |  |  |
Original Building |  | 12,943,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 12,723,000 |  |  |  |
Land and Improvements |  | 2,395,000 |  |  |  |
Building and Improvements |  | 24,570,000 |  |  |  |
Total |  | 26,965,000 |  |  |  |
Accumulated Depreciation |  | $ 16,847,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Lexington Office Park | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 998,000 |  |  |  |
Original Building |  | 1,426,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 19,924,000 |  |  |  |
Land and Improvements |  | 1,263,000 |  |  |  |
Building and Improvements |  | 19,470,000 |  |  |  |
Land held for development |  | 1,615,000 |  |  |  |
Total |  | 22,348,000 |  |  |  |
Accumulated Depreciation |  | $ 17,200,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
The Point | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 6,395,000 |  |  |  |
Original Building |  | 10,040,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 546,000 |  |  |  |
Land and Improvements |  | 6,492,000 |  |  |  |
Building and Improvements |  | 10,489,000 |  |  |  |
Total |  | 16,981,000 |  |  |  |
Accumulated Depreciation |  | $ 2,638,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
690 Folsom Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 3,219,000 |  |  |  |
Original Building |  | 11,038,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,877,000 |  |  |  |
Land and Improvements |  | 3,219,000 |  |  |  |
Building and Improvements |  | 12,915,000 |  |  |  |
Total |  | 16,134,000 |  |  |  |
Accumulated Depreciation |  | $ 4,280,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
33 Hayden Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 266,000 |  |  |  |
Original Building |  | 3,234,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 11,502,000 |  |  |  |
Land and Improvements |  | 425,000 |  |  |  |
Building and Improvements |  | 14,577,000 |  |  |  |
Total |  | 15,002,000 |  |  |  |
Accumulated Depreciation |  | $ 9,090,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
The Avant Retail | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 1,499,000 |  |  |  |
Original Building |  | 6,647,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 2,577,000 |  |  |  |
Land and Improvements |  | 1,499,000 |  |  |  |
Building and Improvements |  | 9,224,000 |  |  |  |
Total |  | 10,723,000 |  |  |  |
Accumulated Depreciation |  | $ 3,587,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
92-100 Hayden Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 594,000 |  |  |  |
Original Building |  | 6,748,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,922,000 |  |  |  |
Land and Improvements |  | 778,000 |  |  |  |
Building and Improvements |  | 8,486,000 |  |  |  |
Total |  | 9,264,000 |  |  |  |
Accumulated Depreciation |  | $ 7,388,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
32 Hartwell Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 168,000 |  |  |  |
Original Building |  | 1,943,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 6,403,000 |  |  |  |
Land and Improvements |  | 314,000 |  |  |  |
Building and Improvements |  | 8,200,000 |  |  |  |
Total |  | 8,514,000 |  |  |  |
Accumulated Depreciation |  | $ 2,931,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
250 Binney Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 110,000 |  |  |  |
Original Building |  | 4,483,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 3,593,000 |  |  |  |
Land and Improvements |  | 273,000 |  |  |  |
Building and Improvements |  | 7,913,000 |  |  |  |
Total |  | 8,186,000 |  |  |  |
Accumulated Depreciation |  | $ 7,244,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
453 Ravendale Drive | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 5,477,000 |  |  |  |
Original Building |  | 1,090,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,286,000 |  |  |  |
Land and Improvements |  | 5,477,000 |  |  |  |
Building and Improvements |  | 2,376,000 |  |  |  |
Total |  | 7,853,000 |  |  |  |
Accumulated Depreciation |  | $ 1,086,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
17 Hartwell Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 26,000 |  |  |  |
Original Building |  | 150,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 6,064,000 |  |  |  |
Land and Improvements |  | 65,000 |  |  |  |
Building and Improvements |  | 6,175,000 |  |  |  |
Total |  | 6,240,000 |  |  |  |
Accumulated Depreciation |  | $ 3,755,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
The Skylyne | Residential Building |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 28,962,000 |  |  |  |
Original Building |  | 239,077,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,792,000 |  |  |  |
Land and Improvements |  | 28,962,000 |  |  |  |
Building and Improvements |  | 240,869,000 |  |  |  |
Total |  | 269,831,000 |  |  |  |
Accumulated Depreciation |  | $ 20,181,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Signature at Reston | Residential Building |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 27,076,000 |  |  |  |
Original Building |  | 190,580,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 3,817,000 |  |  |  |
Land and Improvements |  | 27,076,000 |  |  |  |
Building and Improvements |  | 194,397,000 |  |  |  |
Total |  | 221,473,000 |  |  |  |
Accumulated Depreciation |  | $ 27,876,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Proto Kendall Square | Residential Building |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 9,243,000 |  |  |  |
Original Building |  | 127,248,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 3,336,000 |  |  |  |
Land and Improvements |  | 9,245,000 |  |  |  |
Building and Improvements |  | 130,582,000 |  |  |  |
Total |  | 139,827,000 |  |  |  |
Accumulated Depreciation |  | $ 17,820,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
The Lofts at Atlantic Wharf | Residential Building |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 3,529,000 |  |  |  |
Original Building |  | 54,891,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 2,509,000 |  |  |  |
Land and Improvements |  | 3,529,000 |  |  |  |
Building and Improvements |  | 57,400,000 |  |  |  |
Total |  | 60,929,000 |  |  |  |
Accumulated Depreciation |  | $ 18,631,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Boston Cambridge Marriott | Hotel [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 478,000 |  |  |  |
Original Building |  | 37,918,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 32,131,000 |  |  |  |
Land and Improvements |  | 1,201,000 |  |  |  |
Building and Improvements |  | 68,697,000 |  |  |  |
Land held for development |  | 629,000 |  |  |  |
Total |  | 70,527,000 |  |  |  |
Accumulated Depreciation |  | $ 53,282,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Kendall Center Green Garage | Garage |  |  |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances | [8] | $ 0 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 0 |  |  |  |
Original Building |  | 35,035,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 7,335,000 |  |  |  |
Land and Improvements |  | 103,000 |  |  |  |
Building and Improvements |  | 42,267,000 |  |  |  |
Total |  | 42,370,000 |  |  |  |
Accumulated Depreciation |  | $ 18,414,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
Kendall Center Yellow Garage | Garage |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 1,256,000 |  |  |  |
Original Building |  | 15,697,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,743,000 |  |  |  |
Land and Improvements |  | 1,434,000 |  |  |  |
Building and Improvements |  | 17,262,000 |  |  |  |
Total |  | 18,696,000 |  |  |  |
Accumulated Depreciation |  | $ 7,857,000 |  |  |  |
Depreciable Lives (Years) | [7] | (1) |  |  |  |
290 Binney | Development |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 243,099,000 |  |  |  |
Land and Improvements |  | 1,054,000 |  |  |  |
Development and Construction in Progress |  | 242,045,000 |  |  |  |
Total |  | $ 243,099,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
180 CityPoint [Member] | Development |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 214,754,000 |  |  |  |
Land and Improvements |  | 10,908,000 |  |  |  |
Building and Improvements |  | 108,970,000 |  |  |  |
Development and Construction in Progress |  | 94,876,000 |  |  |  |
Total |  | 214,754,000 |  |  |  |
Accumulated Depreciation |  | $ 541,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
300 Binney Street | Development |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 18,080,000 |  |  |  |
Original Building |  | 51,262,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 38,454,000 |  |  |  |
Land and Improvements |  | 18,080,000 |  |  |  |
Building and Improvements |  | 27,805,000 |  |  |  |
Development and Construction in Progress |  | 61,911,000 |  |  |  |
Total |  | 107,796,000 |  |  |  |
Accumulated Depreciation |  | $ 6,719,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
103 CityPoint | Development |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 88,190,000 |  |  |  |
Land and Improvements |  | 4,672,000 |  |  |  |
Building and Improvements |  | 3,025,000 |  |  |  |
Land held for development |  | 8,672,000 |  |  |  |
Development and Construction in Progress |  | 71,821,000 |  |  |  |
Total |  | 88,190,000 |  |  |  |
Accumulated Depreciation |  | $ 18,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Reston Next Office Phase II | Development |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 39,201,000 |  |  |  |
Development and Construction in Progress |  | 39,201,000 |  |  |  |
Total |  | $ 39,201,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Reston Next Retail | Development |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 8,367,000 |  |  |  |
Development and Construction in Progress |  | 8,367,000 |  |  |  |
Total |  | $ 8,367,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
343 Madison Avenue | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 206,052,000 |  |  |  |
Land and Improvements |  | 158,885,000 |  |  |  |
Land held for development |  | 47,167,000 |  |  |  |
Total |  | $ 206,052,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
777 Harrison Street | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 144,647,000 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 28,334,000 |  |  |  |
Building and Improvements |  | 47,000 |  |  |  |
Land held for development |  | 172,934,000 |  |  |  |
Total |  | 172,981,000 |  |  |  |
Accumulated Depreciation |  | $ 29,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Back Bay Station Master Plan | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 78,150,000 |  |  |  |
Land held for development |  | 78,150,000 |  |  |  |
Total |  | $ 78,150,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
3625 - 3635 Peterson Way | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 63,206,000 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 5,173,000 |  |  |  |
Land held for development |  | 68,379,000 |  |  |  |
Total |  | $ 68,379,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Kendall Center Master Plan | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 48,857,000 |  |  |  |
Land held for development |  | 48,857,000 |  |  |  |
Total |  | $ 48,857,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
North First Master Plan | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 35,004,000 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 4,068,000 |  |  |  |
Land held for development |  | 39,072,000 |  |  |  |
Total |  | $ 39,072,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Plaza at Almaden | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 38,163,000 |  |  |  |
Land held for development |  | 38,163,000 |  |  |  |
Total |  | $ 38,163,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
CityPoint South Master Plan | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 25,594,000 |  |  |  |
Land held for development |  | 25,594,000 |  |  |  |
Total |  | $ 25,594,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Springfield Metro Center | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 19,896,000 |  |  |  |
Land held for development |  | 19,896,000 |  |  |  |
Total |  | $ 19,896,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Reston Gateway Master Plan | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 13,908,000 |  |  |  |
Land held for development |  | 13,908,000 |  |  |  |
Total |  | $ 13,908,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Weston Quarry | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,249,000 |  |  |  |
Land held for development |  | 1,249,000 |  |  |  |
Total |  | $ 1,249,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Broad Run Business Park | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,186,000 |  |  |  |
Land held for development |  | 1,186,000 |  |  |  |
Total |  | $ 1,186,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Reston Overlook Master Plan | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 80,000 |  |  |  |
Land held for development |  | 80,000 |  |  |  |
Total |  | $ 80,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership |  |  |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances | [9] | $ 4,166,379,000 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 5,637,035,000 |  |  |  |
Original Building |  | 15,478,086,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 5,940,085,000 |  |  |  |
Land and Improvements | [10] | 5,859,089,000 |  |  |  |
Building and Improvements | [11] | 19,951,776,000 |  |  |  |
Land held for development | [5] | 697,061,000 | [12] | 721,501,000 |  |
Development and Construction in Progress |  | 547,280,000 |  | 406,574,000 |  |
Total |  | 27,055,206,000 |  | 25,376,700,000 | 23,734,833,000 | 22,926,494,000
Accumulated Depreciation |  | 6,718,037,000 |  | 6,143,384,000 | $ 5,736,240,000 | $ 5,396,111,000
Furniture, Fixtures and Equipment |  | 53,716,000 |  | 50,310,000 |  |
Aggregate cost for tax purpose |  | 28,200,000,000 |  |  |  |
Real Estate Aggregate Accumulated Depreciation For Tax Purposes |  | 6,600,000,000 |  |  |  |
Debt Issuance Costs, Net |  | (33,600,000) |  |  |  |
Right-of-use assets - finance leases |  | 401,680,000 | [6] | 237,510,000 |  |
Operating Lease, Right-of-Use Asset | [6] | $ 324,298,000 |  | $ 167,351,000 |  |
Boston Properties Limited Partnership | Maximum [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Real Estate and Accumulated Depreciation, Life Used for Depreciation |  | 40 years |  |  |  |
Boston Properties Limited Partnership | Furniture, fixtures, and equipment |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Accumulated Depreciation Related to Furniture, Fixtures and Equipment |  | $ 40,324,000 |  |  |  |
Boston Properties Limited Partnership | Land and Land Improvements [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Right-of-use assets - finance leases |  | 378,276,000 |  |  |  |
Operating Lease, Right-of-Use Asset |  | 324,298,000 |  |  |  |
Boston Properties Limited Partnership | Buildings and improvements |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Right-of-use assets - finance leases |  | 23,404,000 |  |  |  |
Boston Properties Limited Partnership | 767Fifth Avenue (the General Motors Building) | Office and Life Sciences Building [Member] |  |  |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances |  | 2,288,004,000 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 1,796,252,000 |  |  |  |
Original Building |  | 1,532,654,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 365,829,000 |  |  |  |
Land and Improvements |  | 1,796,252,000 |  |  |  |
Building and Improvements |  | 1,898,483,000 |  |  |  |
Total |  | 3,694,735,000 |  |  |  |
Accumulated Depreciation |  | $ 507,660,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Prudential Center | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 92,077,000 |  |  |  |
Original Building |  | 948,357,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 732,224,000 |  |  |  |
Land and Improvements |  | 100,535,000 |  |  |  |
Building and Improvements |  | 1,643,064,000 |  |  |  |
Development and Construction in Progress |  | 29,059,000 |  |  |  |
Total |  | 1,772,658,000 |  |  |  |
Accumulated Depreciation |  | $ 754,356,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Embarcadero Center | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 179,697,000 |  |  |  |
Original Building |  | 847,410,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 462,102,000 |  |  |  |
Land and Improvements |  | 180,419,000 |  |  |  |
Building and Improvements |  | 1,308,790,000 |  |  |  |
Total |  | 1,489,209,000 |  |  |  |
Accumulated Depreciation |  | $ 760,144,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 399 Park Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 339,200,000 |  |  |  |
Original Building |  | 700,358,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 349,238,000 |  |  |  |
Land and Improvements |  | 339,200,000 |  |  |  |
Building and Improvements |  | 1,049,596,000 |  |  |  |
Total |  | 1,388,796,000 |  |  |  |
Accumulated Depreciation |  | $ 462,543,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 601 Lexington Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances |  | $ 989,181,000 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 241,600,000 |  |  |  |
Original Building |  | 494,782,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 508,526,000 |  |  |  |
Land and Improvements |  | 279,281,000 |  |  |  |
Building and Improvements |  | 965,627,000 |  |  |  |
Total |  | 1,244,908,000 |  |  |  |
Accumulated Depreciation |  | $ 360,656,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Salesforce Tower | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 200,349,000 |  |  |  |
Original Building |  | 946,205,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 7,623,000 |  |  |  |
Land and Improvements |  | 200,349,000 |  |  |  |
Building and Improvements |  | 953,828,000 |  |  |  |
Total |  | 1,154,177,000 |  |  |  |
Accumulated Depreciation |  | $ 159,274,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 200 Clarendon Street and Garage | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 219,543,000 |  |  |  |
Original Building |  | 667,884,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 251,372,000 |  |  |  |
Land and Improvements |  | 250,910,000 |  |  |  |
Building and Improvements |  | 887,889,000 |  |  |  |
Total |  | 1,138,799,000 |  |  |  |
Accumulated Depreciation |  | $ 338,529,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 250 West 55th Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 285,263,000 |  |  |  |
Original Building |  | 603,167,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 52,917,000 |  |  |  |
Land and Improvements |  | 285,263,000 |  |  |  |
Building and Improvements |  | 656,084,000 |  |  |  |
Total |  | 941,347,000 |  |  |  |
Accumulated Depreciation |  | $ 198,081,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 100 Federal Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 131,067,000 |  |  |  |
Original Building |  | 435,954,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 127,199,000 |  |  |  |
Land and Improvements |  | 131,067,000 |  |  |  |
Building and Improvements |  | 563,153,000 |  |  |  |
Total |  | 694,220,000 |  |  |  |
Accumulated Depreciation |  | $ 172,079,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Times Square Tower | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 165,413,000 |  |  |  |
Original Building |  | 380,438,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 102,302,000 |  |  |  |
Land and Improvements |  | 159,694,000 |  |  |  |
Building and Improvements |  | 488,459,000 |  |  |  |
Total |  | 648,153,000 |  |  |  |
Accumulated Depreciation |  | $ 244,067,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Madison Centre | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 104,641,000 |  |  |  |
Original Building |  | 564,336,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 4,082,000 |  |  |  |
Land and Improvements |  | 104,641,000 |  |  |  |
Building and Improvements |  | 568,418,000 |  |  |  |
Total |  | 673,059,000 |  |  |  |
Accumulated Depreciation |  | $ 35,516,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Carnegie Center | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 142,666,000 |  |  |  |
Original Building |  | 316,856,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 162,582,000 |  |  |  |
Land and Improvements |  | 90,501,000 |  |  |  |
Building and Improvements |  | 472,803,000 |  |  |  |
Land held for development |  | 58,800,000 |  |  |  |
Total |  | 622,104,000 |  |  |  |
Accumulated Depreciation |  | $ 262,096,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Santa Monica Business Park [Member] | Office and Life Sciences Building [Member] |  |  |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances |  | $ 295,649,000 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 46,360,000 |  |  |  |
Original Building |  | 410,421,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 164,229,000 |  |  |  |
Land and Improvements |  | 210,471,000 |  |  |  |
Building and Improvements |  | 410,535,000 |  |  |  |
Land held for development |  | 4,000 |  |  |  |
Total |  | 621,010,000 |  |  |  |
Accumulated Depreciation |  | $ 865,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Reston Next | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 35,549,000 |  |  |  |
Original Building |  | 525,277,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 0 |  |  |  |
Land and Improvements |  | 2,901,000 |  |  |  |
Building and Improvements |  | 557,925,000 |  |  |  |
Total |  | 560,826,000 |  |  |  |
Accumulated Depreciation |  | $ 32,504,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 125 Broadway | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 126,364,000 |  |  |  |
Original Building |  | 433,662,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 4,000,000 |  |  |  |
Land and Improvements |  | 126,364,000 |  |  |  |
Building and Improvements |  | 437,662,000 |  |  |  |
Total |  | 564,026,000 |  |  |  |
Accumulated Depreciation |  | $ 20,717,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Atlantic Wharf | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 63,988,000 |  |  |  |
Original Building |  | 454,537,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 39,399,000 |  |  |  |
Land and Improvements |  | 63,988,000 |  |  |  |
Building and Improvements |  | 493,936,000 |  |  |  |
Total |  | 557,924,000 |  |  |  |
Accumulated Depreciation |  | $ 180,686,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 2100 Pennsylvania Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 185,203,000 |  |  |  |
Original Building |  | 324,206,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 0 |  |  |  |
Land and Improvements |  | 185,203,000 |  |  |  |
Building and Improvements |  | 324,206,000 |  |  |  |
Total |  | 509,409,000 |  |  |  |
Accumulated Depreciation |  | $ 20,768,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 599 Lexington Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 81,040,000 |  |  |  |
Original Building |  | 100,507,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 231,417,000 |  |  |  |
Land and Improvements |  | 81,040,000 |  |  |  |
Building and Improvements |  | 331,924,000 |  |  |  |
Total |  | 412,964,000 |  |  |  |
Accumulated Depreciation |  | $ 188,193,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Fountain Square | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 56,853,000 |  |  |  |
Original Building |  | 306,298,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 49,874,000 |  |  |  |
Land and Improvements |  | 56,853,000 |  |  |  |
Building and Improvements |  | 356,172,000 |  |  |  |
Total |  | 413,025,000 |  |  |  |
Accumulated Depreciation |  | $ 111,481,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 510 Madison Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 103,000,000 |  |  |  |
Original Building |  | 253,665,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 33,100,000 |  |  |  |
Land and Improvements |  | 103,000,000 |  |  |  |
Building and Improvements |  | 286,765,000 |  |  |  |
Total |  | 389,765,000 |  |  |  |
Accumulated Depreciation |  | $ 104,052,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 325 Main Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances | [14] | $ 0 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 21,596,000 |  |  |  |
Original Building |  | 312,492,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 30,740,000 |  |  |  |
Land and Improvements |  | 21,403,000 |  |  |  |
Building and Improvements |  | 343,425,000 |  |  |  |
Total |  | 364,828,000 |  |  |  |
Accumulated Depreciation |  | $ 14,833,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 680 Folsom Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 72,545,000 |  |  |  |
Original Building |  | 219,766,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 8,026,000 |  |  |  |
Land and Improvements |  | 72,545,000 |  |  |  |
Building and Improvements |  | 227,792,000 |  |  |  |
Total |  | 300,337,000 |  |  |  |
Accumulated Depreciation |  | $ 80,964,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 145 Broadway | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 121,000 |  |  |  |
Original Building |  | 273,013,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 26,156,000 |  |  |  |
Land and Improvements |  | 23,164,000 |  |  |  |
Building and Improvements |  | 276,126,000 |  |  |  |
Total |  | 299,290,000 |  |  |  |
Accumulated Depreciation |  | $ 35,390,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 2200 Pennsylvania Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 183,541,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 114,090,000 |  |  |  |
Land and Improvements |  | 102,979,000 |  |  |  |
Building and Improvements |  | 194,652,000 |  |  |  |
Total |  | 297,631,000 |  |  |  |
Accumulated Depreciation |  | $ 77,357,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | South of Market and Democracy Tower | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 13,603,000 |  |  |  |
Original Building |  | 237,479,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 30,616,000 |  |  |  |
Land and Improvements |  | 13,603,000 |  |  |  |
Building and Improvements |  | 268,095,000 |  |  |  |
Total |  | 281,698,000 |  |  |  |
Accumulated Depreciation |  | $ 108,875,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Bay Colony Corporate Center | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 18,789,000 |  |  |  |
Original Building |  | 148,451,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 96,639,000 |  |  |  |
Land and Improvements |  | 18,789,000 |  |  |  |
Building and Improvements |  | 240,416,000 |  |  |  |
Land held for development |  | 4,674,000 |  |  |  |
Total |  | 263,879,000 |  |  |  |
Accumulated Depreciation |  | $ 113,123,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 535 Mission Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 40,933,000 |  |  |  |
Original Building |  | 148,378,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 4,629,000 |  |  |  |
Land and Improvements |  | 40,934,000 |  |  |  |
Building and Improvements |  | 153,006,000 |  |  |  |
Total |  | 193,940,000 |  |  |  |
Accumulated Depreciation |  | $ 46,615,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Mountain View Research Park | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 95,066,000 |  |  |  |
Original Building |  | 68,373,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 21,069,000 |  |  |  |
Land and Improvements |  | 95,066,000 |  |  |  |
Building and Improvements |  | 89,442,000 |  |  |  |
Total |  | 184,508,000 |  |  |  |
Accumulated Depreciation |  | $ 33,095,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Reservoir Place | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 18,605,000 |  |  |  |
Original Building |  | 104,124,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 52,085,000 |  |  |  |
Land and Improvements |  | 19,089,000 |  |  |  |
Building and Improvements |  | 153,898,000 |  |  |  |
Land held for development |  | 1,827,000 |  |  |  |
Total |  | 174,814,000 |  |  |  |
Accumulated Depreciation |  | $ 89,426,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 140 Kendrick Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 18,095,000 |  |  |  |
Original Building |  | 66,905,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 67,871,000 |  |  |  |
Land and Improvements |  | 18,095,000 |  |  |  |
Building and Improvements |  | 134,776,000 |  |  |  |
Total |  | 152,871,000 |  |  |  |
Accumulated Depreciation |  | $ 45,233,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 1330 Connecticut Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 25,982,000 |  |  |  |
Original Building |  | 82,311,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 35,311,000 |  |  |  |
Land and Improvements |  | 25,982,000 |  |  |  |
Building and Improvements |  | 117,622,000 |  |  |  |
Total |  | 143,604,000 |  |  |  |
Accumulated Depreciation |  | $ 51,767,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 880 Winter Street [Member] | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 15,597,000 |  |  |  |
Original Building |  | 37,255,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 95,265,000 |  |  |  |
Land and Improvements |  | 15,597,000 |  |  |  |
Building and Improvements |  | 132,520,000 |  |  |  |
Total |  | 148,117,000 |  |  |  |
Accumulated Depreciation |  | $ 10,056,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | One Freedom Square | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 9,929,000 |  |  |  |
Original Building |  | 84,504,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 43,348,000 |  |  |  |
Land and Improvements |  | 9,883,000 |  |  |  |
Building and Improvements |  | 127,898,000 |  |  |  |
Total |  | 137,781,000 |  |  |  |
Accumulated Depreciation |  | $ 66,495,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Two Freedom Square | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 13,930,000 |  |  |  |
Original Building |  | 77,739,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 38,856,000 |  |  |  |
Land and Improvements |  | 13,866,000 |  |  |  |
Building and Improvements |  | 116,659,000 |  |  |  |
Total |  | 130,525,000 |  |  |  |
Accumulated Depreciation |  | $ 42,556,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Kingstowne Towne Center | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 18,021,000 |  |  |  |
Original Building |  | 109,038,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 4,501,000 |  |  |  |
Land and Improvements |  | 18,021,000 |  |  |  |
Building and Improvements |  | 113,539,000 |  |  |  |
Total |  | 131,560,000 |  |  |  |
Accumulated Depreciation |  | $ 54,432,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | One and Two Reston Overlook | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 16,456,000 |  |  |  |
Original Building |  | 66,192,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 40,806,000 |  |  |  |
Land and Improvements |  | 15,074,000 |  |  |  |
Building and Improvements |  | 108,380,000 |  |  |  |
Total |  | 123,454,000 |  |  |  |
Accumulated Depreciation |  | $ 60,074,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Shady Grove Innovation District [Member] | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 52,030,000 |  |  |  |
Original Building |  | 64,212,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 10,676,000 |  |  |  |
Land and Improvements |  | 26,834,000 |  |  |  |
Building and Improvements |  | 34,954,000 |  |  |  |
Land held for development |  | 65,130,000 |  |  |  |
Total |  | 126,918,000 |  |  |  |
Accumulated Depreciation |  | $ 4,701,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Weston Corporate Center | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 25,753,000 |  |  |  |
Original Building |  | 92,312,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,038,000 |  |  |  |
Land and Improvements |  | 25,854,000 |  |  |  |
Building and Improvements |  | 93,249,000 |  |  |  |
Total |  | 119,103,000 |  |  |  |
Accumulated Depreciation |  | $ 41,485,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 355 Main Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances |  | $ 593,545,000 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 18,863,000 |  |  |  |
Original Building |  | 53,346,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 41,474,000 |  |  |  |
Land and Improvements |  | 21,098,000 |  |  |  |
Building and Improvements |  | 92,585,000 |  |  |  |
Total |  | 113,683,000 |  |  |  |
Accumulated Depreciation |  | $ 36,858,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 17Fifty Presidents Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 113,362,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 162,000 |  |  |  |
Land and Improvements |  | 0 |  |  |  |
Building and Improvements |  | 113,524,000 |  |  |  |
Total |  | 113,524,000 |  |  |  |
Accumulated Depreciation |  | $ 16,624,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 200 West Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 16,148,000 |  |  |  |
Original Building |  | 24,983,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 68,538,000 |  |  |  |
Land and Improvements |  | 16,148,000 |  |  |  |
Building and Improvements |  | 93,164,000 |  |  |  |
Land held for development |  | 357,000 |  |  |  |
Total |  | 109,669,000 |  |  |  |
Accumulated Depreciation |  | $ 27,290,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Discovery Square | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 11,198,000 |  |  |  |
Original Building |  | 71,782,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 16,199,000 |  |  |  |
Land and Improvements |  | 11,146,000 |  |  |  |
Building and Improvements |  | 88,033,000 |  |  |  |
Total |  | 99,179,000 |  |  |  |
Accumulated Depreciation |  | $ 55,135,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 10 CityPoint | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 1,953,000 |  |  |  |
Original Building |  | 85,752,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 7,410,000 |  |  |  |
Land and Improvements |  | 2,127,000 |  |  |  |
Building and Improvements |  | 92,988,000 |  |  |  |
Total |  | 95,115,000 |  |  |  |
Accumulated Depreciation |  | $ 24,003,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 90 Broadway | Office and Life Sciences Building [Member] |  |  |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances | [14] | $ 0 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 19,104,000 |  |  |  |
Original Building |  | 52,078,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 22,563,000 |  |  |  |
Land and Improvements |  | 20,741,000 |  |  |  |
Building and Improvements |  | 73,004,000 |  |  |  |
Total |  | 93,745,000 |  |  |  |
Accumulated Depreciation |  | $ 31,484,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Waltham Weston Corporate Center | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 10,385,000 |  |  |  |
Original Building |  | 60,694,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 17,718,000 |  |  |  |
Land and Improvements |  | 10,350,000 |  |  |  |
Building and Improvements |  | 78,447,000 |  |  |  |
Total |  | 88,797,000 |  |  |  |
Accumulated Depreciation |  | $ 44,588,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 153 & 211 Second Avenue [Member] | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 33,233,000 |  |  |  |
Original Building |  | 55,940,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 718,000 |  |  |  |
Land and Improvements |  | 33,233,000 |  |  |  |
Building and Improvements |  | 55,940,000 |  |  |  |
Land held for development |  | 718,000 |  |  |  |
Total |  | 89,891,000 |  |  |  |
Accumulated Depreciation |  | $ 6,186,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 230 CityPoint | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 13,189,000 |  |  |  |
Original Building |  | 49,823,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 22,680,000 |  |  |  |
Land and Improvements |  | 13,403,000 |  |  |  |
Building and Improvements |  | 72,289,000 |  |  |  |
Total |  | 85,692,000 |  |  |  |
Accumulated Depreciation |  | $ 40,413,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 20 Citypoint | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 4,887,000 |  |  |  |
Original Building |  | 72,764,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 7,072,000 |  |  |  |
Land and Improvements |  | 4,887,000 |  |  |  |
Building and Improvements |  | 79,836,000 |  |  |  |
Total |  | 84,723,000 |  |  |  |
Accumulated Depreciation |  | $ 13,031,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Sumner Square | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 624,000 |  |  |  |
Original Building |  | 28,745,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 49,173,000 |  |  |  |
Land and Improvements |  | 27,317,000 |  |  |  |
Building and Improvements |  | 51,225,000 |  |  |  |
Total |  | 78,542,000 |  |  |  |
Accumulated Depreciation |  | $ 32,209,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 77 CityPoint | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 13,847,000 |  |  |  |
Original Building |  | 60,383,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,401,000 |  |  |  |
Land and Improvements |  | 13,997,000 |  |  |  |
Building and Improvements |  | 61,634,000 |  |  |  |
Total |  | 75,631,000 |  |  |  |
Accumulated Depreciation |  | $ 26,911,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 2440 West El Camino Real | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 16,741,000 |  |  |  |
Original Building |  | 51,285,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 6,565,000 |  |  |  |
Land and Improvements |  | 16,741,000 |  |  |  |
Building and Improvements |  | 57,850,000 |  |  |  |
Total |  | 74,591,000 |  |  |  |
Accumulated Depreciation |  | $ 21,469,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Wisconsin Place | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 53,349,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 13,834,000 |  |  |  |
Land and Improvements |  | 0 |  |  |  |
Building and Improvements |  | 67,183,000 |  |  |  |
Total |  | 67,183,000 |  |  |  |
Accumulated Depreciation |  | $ 28,960,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Reston Corporate Center | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 9,135,000 |  |  |  |
Original Building |  | 50,857,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,878,000 |  |  |  |
Land and Improvements |  | 9,496,000 |  |  |  |
Building and Improvements |  | 52,374,000 |  |  |  |
Total |  | 61,870,000 |  |  |  |
Accumulated Depreciation |  | $ 33,309,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 255 Main Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 134,000 |  |  |  |
Original Building |  | 25,110,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 31,674,000 |  |  |  |
Land and Improvements |  | 134,000 |  |  |  |
Building and Improvements |  | 56,784,000 |  |  |  |
Total |  | 56,918,000 |  |  |  |
Accumulated Depreciation |  | $ 43,368,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | University Place | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 37,091,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 14,318,000 |  |  |  |
Land and Improvements |  | 4,807,000 |  |  |  |
Building and Improvements |  | 46,602,000 |  |  |  |
Total |  | 51,409,000 |  |  |  |
Accumulated Depreciation |  | $ 36,037,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 890 Winter Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 13,913,000 |  |  |  |
Original Building |  | 28,557,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 8,507,000 |  |  |  |
Land and Improvements |  | 13,913,000 |  |  |  |
Building and Improvements |  | 37,064,000 |  |  |  |
Total |  | 50,977,000 |  |  |  |
Accumulated Depreciation |  | $ 7,296,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Capital Gallery | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 4,725,000 |  |  |  |
Original Building |  | 29,565,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 5,698,000 |  |  |  |
Land and Improvements |  | 6,128,000 |  |  |  |
Building and Improvements |  | 33,860,000 |  |  |  |
Total |  | 39,988,000 |  |  |  |
Accumulated Depreciation |  | $ 22,801,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | North First Business Park | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 23,398,000 |  |  |  |
Original Building |  | 13,069,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 5,235,000 |  |  |  |
Land and Improvements |  | 23,372,000 |  |  |  |
Building and Improvements |  | 18,330,000 |  |  |  |
Total |  | 41,702,000 |  |  |  |
Accumulated Depreciation |  | $ 17,347,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 150 Broadway | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 850,000 |  |  |  |
Original Building |  | 25,042,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 13,744,000 |  |  |  |
Land and Improvements |  | 822,000 |  |  |  |
Building and Improvements |  | 38,814,000 |  |  |  |
Total |  | 39,636,000 |  |  |  |
Accumulated Depreciation |  | $ 17,823,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 105 Broadway | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 1,299,000 |  |  |  |
Original Building |  | 12,943,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 10,617,000 |  |  |  |
Land and Improvements |  | 1,868,000 |  |  |  |
Building and Improvements |  | 22,991,000 |  |  |  |
Total |  | 24,859,000 |  |  |  |
Accumulated Depreciation |  | $ 16,133,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Lexington Office Park | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 998,000 |  |  |  |
Original Building |  | 1,426,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 19,160,000 |  |  |  |
Land and Improvements |  | 1,072,000 |  |  |  |
Building and Improvements |  | 18,897,000 |  |  |  |
Land held for development |  | 1,615,000 |  |  |  |
Total |  | 21,584,000 |  |  |  |
Accumulated Depreciation |  | $ 16,945,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | The Point | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 6,395,000 |  |  |  |
Original Building |  | 10,040,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 546,000 |  |  |  |
Land and Improvements |  | 6,492,000 |  |  |  |
Building and Improvements |  | 10,489,000 |  |  |  |
Total |  | 16,981,000 |  |  |  |
Accumulated Depreciation |  | $ 2,638,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 690 Folsom Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 3,219,000 |  |  |  |
Original Building |  | 11,038,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,877,000 |  |  |  |
Land and Improvements |  | 3,219,000 |  |  |  |
Building and Improvements |  | 12,915,000 |  |  |  |
Total |  | 16,134,000 |  |  |  |
Accumulated Depreciation |  | $ 4,280,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 33 Hayden Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 266,000 |  |  |  |
Original Building |  | 3,234,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 10,865,000 |  |  |  |
Land and Improvements |  | 266,000 |  |  |  |
Building and Improvements |  | 14,099,000 |  |  |  |
Total |  | 14,365,000 |  |  |  |
Accumulated Depreciation |  | $ 8,873,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | The Avant Retail | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 1,499,000 |  |  |  |
Original Building |  | 6,647,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 2,577,000 |  |  |  |
Land and Improvements |  | 1,499,000 |  |  |  |
Building and Improvements |  | 9,224,000 |  |  |  |
Total |  | 10,723,000 |  |  |  |
Accumulated Depreciation |  | $ 3,587,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 92-100 Hayden Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 594,000 |  |  |  |
Original Building |  | 6,748,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,193,000 |  |  |  |
Land and Improvements |  | 595,000 |  |  |  |
Building and Improvements |  | 7,940,000 |  |  |  |
Total |  | 8,535,000 |  |  |  |
Accumulated Depreciation |  | $ 7,140,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 32 Hartwell Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 168,000 |  |  |  |
Original Building |  | 1,943,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 5,817,000 |  |  |  |
Land and Improvements |  | 168,000 |  |  |  |
Building and Improvements |  | 7,760,000 |  |  |  |
Total |  | 7,928,000 |  |  |  |
Accumulated Depreciation |  | $ 2,731,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 250 Binney Street | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 110,000 |  |  |  |
Original Building |  | 4,483,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 2,939,000 |  |  |  |
Land and Improvements |  | 110,000 |  |  |  |
Building and Improvements |  | 7,422,000 |  |  |  |
Total |  | 7,532,000 |  |  |  |
Accumulated Depreciation |  | $ 7,026,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 453 Ravendale Drive | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 5,477,000 |  |  |  |
Original Building |  | 1,090,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,286,000 |  |  |  |
Land and Improvements |  | 5,477,000 |  |  |  |
Building and Improvements |  | 2,376,000 |  |  |  |
Total |  | 7,853,000 |  |  |  |
Accumulated Depreciation |  | $ 1,086,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 17 Hartwell Avenue | Office and Life Sciences Building [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 26,000 |  |  |  |
Original Building |  | 150,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 5,907,000 |  |  |  |
Land and Improvements |  | 26,000 |  |  |  |
Building and Improvements |  | 6,057,000 |  |  |  |
Total |  | 6,083,000 |  |  |  |
Accumulated Depreciation |  | $ 3,701,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | The Skylyne | Residential Building |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 28,962,000 |  |  |  |
Original Building |  | 239,077,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,792,000 |  |  |  |
Land and Improvements |  | 28,962,000 |  |  |  |
Building and Improvements |  | 240,869,000 |  |  |  |
Total |  | 269,831,000 |  |  |  |
Accumulated Depreciation |  | $ 20,181,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Signature at Reston | Residential Building |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 27,076,000 |  |  |  |
Original Building |  | 190,580,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 3,817,000 |  |  |  |
Land and Improvements |  | 27,076,000 |  |  |  |
Building and Improvements |  | 194,397,000 |  |  |  |
Total |  | 221,473,000 |  |  |  |
Accumulated Depreciation |  | $ 27,876,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Proto Kendall Square | Residential Building |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 9,243,000 |  |  |  |
Original Building |  | 127,248,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 3,336,000 |  |  |  |
Land and Improvements |  | 9,245,000 |  |  |  |
Building and Improvements |  | 130,582,000 |  |  |  |
Total |  | 139,827,000 |  |  |  |
Accumulated Depreciation |  | $ 17,820,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | The Lofts at Atlantic Wharf | Residential Building |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 3,529,000 |  |  |  |
Original Building |  | 54,891,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 2,509,000 |  |  |  |
Land and Improvements |  | 3,529,000 |  |  |  |
Building and Improvements |  | 57,400,000 |  |  |  |
Total |  | 60,929,000 |  |  |  |
Accumulated Depreciation |  | $ 18,631,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Boston Cambridge Marriott | Hotel [Member] |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 478,000 |  |  |  |
Original Building |  | 37,918,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 29,240,000 |  |  |  |
Land and Improvements |  | 478,000 |  |  |  |
Building and Improvements |  | 66,529,000 |  |  |  |
Land held for development |  | 629,000 |  |  |  |
Total |  | 67,636,000 |  |  |  |
Accumulated Depreciation |  | $ 52,302,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Kendall Center Green Garage | Garage |  |  |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |  |  |
Encumbrances | [14] | $ 0 |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | 0 |  |  |  |
Original Building |  | 35,035,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 6,921,000 |  |  |  |
Building and Improvements |  | 41,956,000 |  |  |  |
Total |  | 41,956,000 |  |  |  |
Accumulated Depreciation |  | $ 18,275,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | Kendall Center Yellow Garage | Garage |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 1,256,000 |  |  |  |
Original Building |  | 15,697,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,031,000 |  |  |  |
Land and Improvements |  | 1,256,000 |  |  |  |
Building and Improvements |  | 16,728,000 |  |  |  |
Total |  | 17,984,000 |  |  |  |
Accumulated Depreciation |  | $ 7,619,000 |  |  |  |
Depreciable Lives (Years) | [13] | (1) |  |  |  |
Boston Properties Limited Partnership | 290 Binney | Development |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 242,683,000 |  |  |  |
Land and Improvements |  | 638,000 |  |  |  |
Development and Construction in Progress |  | 242,045,000 |  |  |  |
Total |  | 242,683,000 |  |  |  |
Accumulated Depreciation |  | $ 0 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | 180 CityPoint [Member] | Development |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 214,754,000 |  |  |  |
Land and Improvements |  | 10,908,000 |  |  |  |
Building and Improvements |  | 108,970,000 |  |  |  |
Development and Construction in Progress |  | 94,876,000 |  |  |  |
Total |  | 214,754,000 |  |  |  |
Accumulated Depreciation |  | $ 541,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | 300 Binney Street | Development |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 18,080,000 |  |  |  |
Original Building |  | 51,262,000 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 38,454,000 |  |  |  |
Land and Improvements |  | 18,080,000 |  |  |  |
Building and Improvements |  | 27,805,000 |  |  |  |
Development and Construction in Progress |  | 61,911,000 |  |  |  |
Total |  | 107,796,000 |  |  |  |
Accumulated Depreciation |  | $ 6,719,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | 103 CityPoint | Development |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 88,188,000 |  |  |  |
Land and Improvements |  | 4,670,000 |  |  |  |
Building and Improvements |  | 3,025,000 |  |  |  |
Land held for development |  | 8,672,000 |  |  |  |
Development and Construction in Progress |  | 71,821,000 |  |  |  |
Total |  | 88,188,000 |  |  |  |
Accumulated Depreciation |  | $ 18,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | Reston Next Office Phase II | Development |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 39,201,000 |  |  |  |
Development and Construction in Progress |  | 39,201,000 |  |  |  |
Total |  | 39,201,000 |  |  |  |
Accumulated Depreciation |  | $ 0 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | Reston Next Retail | Development |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 8,367,000 |  |  |  |
Development and Construction in Progress |  | 8,367,000 |  |  |  |
Total |  | 8,367,000 |  |  |  |
Accumulated Depreciation |  | $ 0 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | 343 Madison Avenue | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 206,052,000 |  |  |  |
Land and Improvements |  | 158,885,000 |  |  |  |
Land held for development |  | 47,167,000 |  |  |  |
Total |  | 206,052,000 |  |  |  |
Accumulated Depreciation |  | $ 0 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | 777 Harrison Street | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 144,647,000 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 28,334,000 |  |  |  |
Building and Improvements |  | 47,000 |  |  |  |
Land held for development |  | 172,934,000 |  |  |  |
Total |  | 172,981,000 |  |  |  |
Accumulated Depreciation |  | $ 29,000 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | Back Bay Station Master Plan | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 78,150,000 |  |  |  |
Land held for development |  | 78,150,000 |  |  |  |
Total |  | 78,150,000 |  |  |  |
Accumulated Depreciation |  | $ 0 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | 3625 - 3635 Peterson Way | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 63,206,000 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 5,173,000 |  |  |  |
Land held for development |  | 68,379,000 |  |  |  |
Total |  | 68,379,000 |  |  |  |
Accumulated Depreciation |  | $ 0 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | Kendall Center Master Plan | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 48,857,000 |  |  |  |
Land held for development |  | 48,857,000 |  |  |  |
Total |  | 48,857,000 |  |  |  |
Accumulated Depreciation |  | $ 0 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | North First Master Plan | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 35,004,000 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 4,068,000 |  |  |  |
Land held for development |  | 39,072,000 |  |  |  |
Total |  | 39,072,000 |  |  |  |
Accumulated Depreciation |  | $ 0 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | Plaza at Almaden | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 38,163,000 |  |  |  |
Land held for development |  | 38,163,000 |  |  |  |
Total |  | 38,163,000 |  |  |  |
Accumulated Depreciation |  | $ 0 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | CityPoint South Master Plan | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 25,594,000 |  |  |  |
Land held for development |  | 25,594,000 |  |  |  |
Total |  | 25,594,000 |  |  |  |
Accumulated Depreciation |  | $ 0 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | Springfield Metro Center | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 19,896,000 |  |  |  |
Land held for development |  | 19,896,000 |  |  |  |
Total |  | 19,896,000 |  |  |  |
Accumulated Depreciation |  | $ 0 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | Reston Gateway Master Plan | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 13,908,000 |  |  |  |
Land held for development |  | 13,908,000 |  |  |  |
Total |  | 13,908,000 |  |  |  |
Accumulated Depreciation |  | $ 0 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | Weston Quarry | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,249,000 |  |  |  |
Land held for development |  | 1,249,000 |  |  |  |
Total |  | 1,249,000 |  |  |  |
Accumulated Depreciation |  | $ 0 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | Broad Run Business Park | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 1,186,000 |  |  |  |
Land held for development |  | 1,186,000 |  |  |  |
Total |  | 1,186,000 |  |  |  |
Accumulated Depreciation |  | $ 0 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
Boston Properties Limited Partnership | Reston Overlook Master Plan | Land |  |  |  |  |  |
Original Cost |  |  |  |  |  |
Original Land |  | $ 0 |  |  |  |
Original Building |  | 0 |  |  |  |
Costs Capitalized Subsequent to Acquisition |  | 80,000 |  |  |  |
Land held for development |  | 80,000 |  |  |  |
Total |  | 80,000 |  |  |  |
Accumulated Depreciation |  | $ 0 |  |  |  |
Depreciable Lives (Years) |  | N/A |  |  |  |
[1] | Includes unamortized deferred financing costs and fair value debt adjustment totaling approximately $(33.6) million.
[2] | Includes Right of Use Assets - Finance Leases and Right of Use Assets - Operating Leases of approximately $378,276 and $324,298, respectively.
[3] | Includes Right of Use Assets - Finance Leases of approximately $23,404.
[4] | Includes pre-development costs.
[5] | Includes pre-development costs.
[6] | See Note 4.
[7] | Depreciation of the buildings and improvements are calculated over lives ranging from the life of the lease to 40 years.
[8] | This property is encumbered with the mortgage note shown at 355 Main Street. See Note 7 to the Consolidated Financial Statements.
[9] | Includes unamortized deferred financing costs and fair value debt adjustment totaling approximately $(33.6) million.
[10] | Includes Right of Use Assets - Finance Leases and Right of Use Assets - Operating Leases of approximately $378,276 and $324,298, respectively.
[11] | Includes Right of Use Assets - Finance Leases of approximately $23,404.
[12] | Includes pre-development costs.
[13] | Depreciation of the buildings and improvements are calculated over lives ranging from the life of the lease to 40 years.
[14] | This property is encumbered with the mortgage note shown at 355 Main Street. See Note 7 to the Consolidated Financial Statements.

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