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SEC Schedule, Article 12-28, Real Estate and Accumulated Depreciation (Details) - USD ($)
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances [1] $ 4,276,609,000      
Original Cost        
Original Land 5,716,458,000      
Original Building 15,848,823,000      
Costs Capitalized Subsequent to Acquisition 6,955,895,000      
Land and Improvements [2] 6,002,805,000      
Building and Improvements [3] 21,039,681,000      
Land held for development [5] 714,050,000 [4] $ 697,061,000    
Development and Construction in Progress 764,640,000 547,280,000    
Total 28,521,176,000 27,421,471,000 $ 25,744,214,000 $ 24,108,220,000
Accumulated Depreciation 7,485,502,000 6,841,404,000 6,260,992,000 5,848,183,000
Furniture, Fixtures and Equipment 57,136,000 53,716,000    
Aggregate cost for tax purpose 25,900,000,000      
Real Estate Aggregate Accumulated Depreciation For Tax Purposes 6,400,000,000      
Debt Issuance Costs, Net (25,700,000)      
Right-of-use assets - finance leases [6] 372,922,000 401,680,000    
Operating Lease, Right-of-Use Asset [6] $ 334,767,000 324,298,000    
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 $ 42,555,000      
Land and Land Improvements [Member]        
Original Cost        
Right-of-use assets - finance leases 349,314,000      
Operating Lease, Right-of-Use Asset 334,767,000      
Buildings and improvements        
Original Cost        
Right-of-use assets - finance leases 23,608,000      
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 2,291,498,000      
Original Cost        
Original Land 1,796,252,000      
Original Building 1,532,654,000      
Costs Capitalized Subsequent to Acquisition 393,520,000      
Land and Improvements 1,796,252,000      
Building and Improvements 1,926,174,000      
Total 3,722,426,000      
Accumulated Depreciation $ 567,621,000      
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 833,604,000      
Land and Improvements 115,632,000      
Building and Improvements 1,758,406,000      
Total 1,874,038,000      
Accumulated Depreciation $ 821,046,000      
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 570,259,000      
Land and Improvements 195,986,000      
Building and Improvements 1,401,380,000      
Total 1,597,366,000      
Accumulated Depreciation $ 829,400,000      
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 419,566,000      
Land and Improvements 354,107,000      
Building and Improvements 1,105,017,000      
Total 1,459,124,000      
Accumulated Depreciation $ 522,555,000      
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 $ 990,529,000      
Original Cost        
Original Land 241,600,000      
Original Building 494,782,000      
Costs Capitalized Subsequent to Acquisition 568,356,000      
Land and Improvements 289,639,000      
Building and Improvements 1,015,099,000      
Total 1,304,738,000      
Accumulated Depreciation $ 398,796,000      
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 288,694,000      
Land and Improvements 257,203,000      
Building and Improvements 918,918,000      
Total 1,176,121,000      
Accumulated Depreciation $ 370,980,000      
Depreciable Lives (Years) [7] (1)      
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 7,655,000      
Land and Improvements 200,349,000      
Building and Improvements 953,860,000      
Total 1,154,209,000      
Accumulated Depreciation $ 188,376,000      
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 51,331,000      
Land and Improvements 285,263,000      
Building and Improvements 654,498,000      
Total 939,761,000      
Accumulated Depreciation $ 215,386,000      
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 138,639,000      
Land and Improvements 131,067,000      
Building and Improvements 574,593,000      
Total 705,660,000      
Accumulated Depreciation $ 189,447,000      
Depreciable Lives (Years) [7] (1)      
7 Times Square | Office and Life Sciences Building [Member]        
Original Cost        
Original Land $ 165,413,000      
Original Building 380,438,000      
Costs Capitalized Subsequent to Acquisition 149,990,000      
Land and Improvements 169,193,000      
Building and Improvements 526,648,000      
Total 695,841,000      
Accumulated Depreciation $ 264,411,000      
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 5,126,000      
Land and Improvements 104,641,000      
Building and Improvements 569,462,000      
Total 674,103,000      
Accumulated Depreciation $ 56,212,000      
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 184,814,000      
Land and Improvements 94,243,000      
Building and Improvements 491,116,000      
Land held for development 58,977,000      
Total 644,336,000      
Accumulated Depreciation $ 279,961,000      
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 $ 198,021,000      
Original Cost        
Original Land 46,360,000      
Original Building 410,421,000      
Costs Capitalized Subsequent to Acquisition 177,576,000      
Land and Improvements 210,471,000      
Building and Improvements 423,775,000      
Land held for development 111,000      
Total 634,357,000      
Accumulated Depreciation $ 18,660,000      
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 5,860,000      
Land and Improvements 2,901,000      
Building and Improvements 563,785,000      
Total 566,686,000      
Accumulated Depreciation $ 51,052,000      
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 42,166,000      
Land and Improvements 63,988,000      
Building and Improvements 496,703,000      
Total 560,691,000      
Accumulated Depreciation $ 195,192,000      
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 4,433,000      
Land and Improvements 185,203,000      
Building and Improvements 328,639,000      
Total 513,842,000      
Accumulated Depreciation $ 34,319,000      
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 269,410,000      
Land and Improvements 87,852,000      
Building and Improvements 363,105,000      
Total 450,957,000      
Accumulated Depreciation $ 212,251,000      
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 56,795,000      
Land and Improvements 56,853,000      
Building and Improvements 363,093,000      
Total 419,946,000      
Accumulated Depreciation $ 125,277,000      
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 37,287,000      
Land and Improvements 103,000,000      
Building and Improvements 290,952,000      
Total 393,952,000      
Accumulated Depreciation $ 111,209,000      
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 42,325,000      
Land and Improvements 21,596,000      
Building and Improvements 354,817,000      
Total 376,413,000      
Accumulated Depreciation $ 25,113,000      
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 12,577,000      
Land and Improvements 72,545,000      
Building and Improvements 232,343,000      
Total 304,888,000      
Accumulated Depreciation $ 87,930,000      
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 26,980,000      
Land and Improvements 23,367,000      
Building and Improvements 276,747,000      
Total 300,114,000      
Accumulated Depreciation $ 43,888,000      
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 116,540,000      
Land and Improvements 101,734,000      
Building and Improvements 198,347,000      
Total 300,081,000      
Accumulated Depreciation $ 75,450,000      
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 31,096,000      
Land and Improvements 13,687,000      
Building and Improvements 268,491,000      
Total 282,178,000      
Accumulated Depreciation $ 118,780,000      
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 95,025,000      
Land and Improvements 18,789,000      
Building and Improvements 238,765,000      
Land held for development 4,711,000      
Total 262,265,000      
Accumulated Depreciation $ 118,253,000      
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 6,325,000      
Land and Improvements 40,934,000      
Building and Improvements 154,702,000      
Total 195,636,000      
Accumulated Depreciation $ 50,973,000      
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 21,315,000      
Land and Improvements 95,066,000      
Building and Improvements 89,688,000      
Total 184,754,000      
Accumulated Depreciation $ 37,048,000      
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 55,829,000      
Land and Improvements 20,108,000      
Building and Improvements 158,450,000      
Total 178,558,000      
Accumulated Depreciation $ 91,828,000      
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 72,615,000      
Land and Improvements 19,092,000      
Building and Improvements 138,523,000      
Total 157,615,000      
Accumulated Depreciation $ 52,387,000      
Depreciable Lives (Years) [7] (1)      
901 New York Avenue | Office and Life Sciences Building [Member]        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances $ 201,692,000      
Original Cost        
Original Land 65,808,000      
Original Building 72,970,000      
Costs Capitalized Subsequent to Acquisition 13,225,000      
Land and Improvements 65,808,000      
Building and Improvements 86,195,000      
Total 152,003,000      
Accumulated Depreciation $ 4,253,000      
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 39,773,000      
Land and Improvements 27,135,000      
Building and Improvements 120,931,000      
Total 148,066,000      
Accumulated Depreciation $ 58,777,000      
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 47,580,000      
Land and Improvements 11,293,000      
Building and Improvements 130,720,000      
Total 142,013,000      
Accumulated Depreciation $ 73,356,000      
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 46,236,000      
Land and Improvements 15,420,000      
Building and Improvements 122,485,000      
Total 137,905,000      
Accumulated Depreciation $ 50,676,000      
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 49,596,000      
Land and Improvements 16,179,000      
Building and Improvements 116,065,000      
Total 132,244,000      
Accumulated Depreciation $ 64,247,000      
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 4,296,000      
Land and Improvements 18,062,000      
Building and Improvements 113,293,000      
Total 131,355,000      
Accumulated Depreciation $ 57,756,000      
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 1,630,000      
Land and Improvements 25,854,000      
Building and Improvements 93,841,000      
Total 119,695,000      
Accumulated Depreciation $ 44,575,000      
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 33,904,000      
Land and Improvements 12,533,000      
Building and Improvements 104,351,000      
Total 116,884,000      
Accumulated Depreciation $ 62,220,000      
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 (284,000)      
Land and Improvements 26,834,000      
Building and Improvements 35,014,000      
Land held for development 54,110,000      
Total 115,958,000      
Accumulated Depreciation $ 5,526,000      
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 $ 594,869,000      
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 $ 39,649,000      
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 $ 21,016,000      
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 7,023,000      
Land and Improvements 2,288,000      
Building and Improvements 92,440,000      
Total 94,728,000      
Accumulated Depreciation $ 26,693,000      
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 22,745,000      
Land and Improvements 11,097,000      
Building and Improvements 82,727,000      
Total 93,824,000      
Accumulated Depreciation $ 48,609,000      
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 22,168,000      
Land and Improvements 20,785,000      
Building and Improvements 72,565,000      
Total 93,350,000      
Accumulated Depreciation $ 33,396,000      
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 60,966,000      
Land and Improvements 27,441,000      
Building and Improvements 62,894,000      
Total 90,335,000      
Accumulated Depreciation $ 29,739,000      
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 25,075,000      
Land and Improvements 13,807,000      
Building and Improvements 74,280,000      
Total 88,087,000      
Accumulated Depreciation $ 41,800,000      
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 10,648,000      
Land and Improvements 14,023,000      
Building and Improvements 70,855,000      
Total 84,878,000      
Accumulated Depreciation $ 30,750,000      
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 $ 16,456,000      
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 26,100,000      
Land and Improvements 0      
Building and Improvements 79,449,000      
Total 79,449,000      
Accumulated Depreciation $ 31,223,000      
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 $ 23,427,000      
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 $ 35,620,000      
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 19,104,000      
Land and Improvements 13,913,000      
Building and Improvements 47,661,000      
Total 61,574,000      
Accumulated Depreciation $ 9,397,000      
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 33,766,000      
Land and Improvements 548,000      
Building and Improvements 58,462,000      
Total 59,010,000      
Accumulated Depreciation $ 45,819,000      
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 15,149,000      
Land and Improvements 4,145,000      
Building and Improvements 48,095,000      
Total 52,240,000      
Accumulated Depreciation $ 38,992,000      
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 10,374,000      
Land and Improvements 8,662,000      
Building and Improvements 36,002,000      
Total 44,664,000      
Accumulated Depreciation $ 25,075,000      
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 6,116,000      
Land and Improvements 23,378,000      
Building and Improvements 19,205,000      
Total 42,583,000      
Accumulated Depreciation $ 17,852,000      
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 $ 20,185,000      
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 $ 18,114,000      
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 19,738,000      
Land and Improvements 1,263,000      
Building and Improvements 19,233,000      
Land held for development 1,666,000      
Total 22,162,000      
Accumulated Depreciation $ 17,298,000      
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 $ 2,969,000      
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 $ 4,723,000      
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 $ 3,885,000      
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 9,206,000      
Land and Improvements 65,000      
Building and Improvements 6,175,000      
Land held for development 3,142,000      
Total 9,382,000      
Accumulated Depreciation $ 3,831,000      
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 6,394,000      
Land and Improvements 314,000      
Building and Improvements 8,191,000      
Total 8,505,000      
Accumulated Depreciation $ 3,291,000      
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 $ 1,300,000      
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 5,580,000      
Land and Improvements 126,364,000      
Building and Improvements 439,242,000      
Total 565,606,000      
Accumulated Depreciation $ 38,051,000      
Depreciable Lives (Years) [7] (1)      
180 CityPoint [Member] | Office and Life Sciences Building [Member]        
Original Cost        
Original Land $ 10,908,000      
Original Building 211,883,000      
Costs Capitalized Subsequent to Acquisition 0      
Land and Improvements 10,908,000      
Building and Improvements 211,883,000      
Total 222,791,000      
Accumulated Depreciation $ 6,212,000      
Depreciable Lives (Years) [7] (1)      
300 Binney Street | Office and Life Sciences Building [Member]        
Original Cost        
Original Land $ 18,080,000      
Original Building 51,262,000      
Costs Capitalized Subsequent to Acquisition 148,974,000      
Land and Improvements 18,080,000      
Building and Improvements 200,236,000      
Total 218,316,000      
Accumulated Depreciation $ 7,923,000      
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 95,615,000      
Land and Improvements 15,597,000      
Building and Improvements 132,870,000      
Total 148,467,000      
Accumulated Depreciation $ 18,179,000      
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 77,709,000      
Land and Improvements 16,813,000      
Building and Improvements 101,670,000      
Land held for development 357,000      
Total 118,840,000      
Accumulated Depreciation $ 33,730,000      
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 2,352,000      
Land and Improvements 33,233,000      
Building and Improvements 58,292,000      
Total 91,525,000      
Accumulated Depreciation $ 7,583,000      
Depreciable Lives (Years) [7] (1)      
103 CityPoint | Office and Life Sciences Building [Member]        
Original Cost        
Original Land $ 4,672,000      
Original Building 77,515,000      
Costs Capitalized Subsequent to Acquisition 0      
Land and Improvements 4,672,000      
Building and Improvements 77,515,000      
Total 82,187,000      
Accumulated Depreciation $ 569,000      
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 $ 7,473,000      
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 $ 10,250,000      
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 1,817,000      
Land and Improvements 778,000      
Building and Improvements 8,381,000      
Total 9,159,000      
Accumulated Depreciation $ 7,456,000      
Depreciable Lives (Years) [7] (1)      
The Skylyne | Residential Building        
Original Cost        
Original Land $ 0      
Original Building 239,077,000      
Costs Capitalized Subsequent to Acquisition 1,792,000      
Land and Improvements 0      
Building and Improvements 240,869,000      
Total 240,869,000      
Accumulated Depreciation $ 26,207,000      
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 2,980,000      
Land and Improvements 27,076,000      
Building and Improvements 193,560,000      
Total 220,636,000      
Accumulated Depreciation $ 32,887,000      
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 $ 21,122,000      
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 2,598,000      
Land and Improvements 3,529,000      
Building and Improvements 57,489,000      
Total 61,018,000      
Accumulated Depreciation $ 20,108,000      
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 30,031,000      
Land and Improvements 1,201,000      
Building and Improvements 66,597,000      
Land held for development 629,000      
Total 68,427,000      
Accumulated Depreciation $ 53,343,000      
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 $ 19,812,000      
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 1,674,000      
Land and Improvements 1,434,000      
Building and Improvements 17,193,000      
Total 18,627,000      
Accumulated Depreciation $ 8,248,000      
Depreciable Lives (Years) [7] (1)      
290 Binney Street | Development        
Original Cost        
Original Land $ 0      
Original Building 0      
Costs Capitalized Subsequent to Acquisition 575,958,000      
Land and Improvements 1,054,000      
Development and Construction in Progress 574,904,000      
Total $ 575,958,000      
Depreciable Lives (Years) N/A      
121 Broadway | Development        
Original Cost        
Original Land $ 0      
Original Building 0      
Costs Capitalized Subsequent to Acquisition 102,843,000      
Development and Construction in Progress 102,843,000      
Total $ 102,843,000      
Depreciable Lives (Years) N/A      
Reston Next Office Phase II | Development        
Original Cost        
Original Land $ 0      
Original Building 0      
Costs Capitalized Subsequent to Acquisition 45,434,000      
Land and Improvements 1,692,000      
Building and Improvements 3,030,000      
Development and Construction in Progress 40,712,000      
Total 45,434,000      
Accumulated Depreciation $ 14,000      
Depreciable Lives (Years) N/A      
725 12th Street | Development        
Original Cost        
Original Land $ 26,997,000      
Original Building 8,369,000      
Costs Capitalized Subsequent to Acquisition 522,000      
Development and Construction in Progress 35,888,000      
Total $ 35,888,000      
Depreciable Lives (Years) N/A      
Reston Next Retail | Development        
Original Cost        
Original Land $ 0      
Original Building 0      
Costs Capitalized Subsequent to Acquisition 10,293,000      
Development and Construction in Progress 10,293,000      
Total $ 10,293,000      
Depreciable Lives (Years) N/A      
343 Madison Avenue | Land        
Original Cost        
Original Land $ 0      
Original Building 0      
Costs Capitalized Subsequent to Acquisition 240,226,000      
Land and Improvements 140,558,000      
Land held for development 99,668,000      
Total $ 240,226,000      
Depreciable Lives (Years) N/A      
777 Harrison Street | Land        
Original Cost        
Original Land $ 144,647,000      
Original Building 0      
Costs Capitalized Subsequent to Acquisition 28,366,000      
Building and Improvements 47,000      
Land held for development 172,966,000      
Total 173,013,000      
Accumulated Depreciation $ 39,000      
Depreciable Lives (Years) N/A      
Back Bay Station Master Plan | Land        
Original Cost        
Original Land $ 0      
Original Building 0      
Costs Capitalized Subsequent to Acquisition 103,908,000      
Land and Improvements 24,808,000      
Land held for development 79,100,000      
Total $ 103,908,000      
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 5,185,000      
Land held for development 68,391,000      
Total $ 68,391,000      
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 4,600,000      
Land held for development 39,604,000      
Total $ 39,604,000      
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 36,522,000      
Land held for development 36,522,000      
Total $ 36,522,000      
Depreciable Lives (Years) N/A      
Springfield Metro Center | Land        
Original Cost        
Original Land $ 0      
Original Building 0      
Costs Capitalized Subsequent to Acquisition 19,913,000      
Land held for development 19,913,000      
Total $ 19,913,000      
Depreciable Lives (Years) N/A      
Reston Gateway Master Plan | Land        
Original Cost        
Original Land $ 0      
Original Building 0      
Costs Capitalized Subsequent to Acquisition 17,199,000      
Land held for development 17,199,000      
Total $ 17,199,000      
Depreciable Lives (Years) N/A      
Kendall Center Master Plan | Land        
Original Cost        
Original Land $ 0      
Original Building 0      
Costs Capitalized Subsequent to Acquisition 16,301,000      
Land held for development 16,301,000      
Total $ 16,301,000      
Depreciable Lives (Years) N/A      
Weston Quarry | Land        
Original Cost        
Original Land $ 0      
Original Building 0      
Costs Capitalized Subsequent to Acquisition 1,252,000      
Land held for development 1,252,000      
Total $ 1,252,000      
Depreciable Lives (Years) N/A      
Broad Run Business Park | Land        
Original Cost        
Original Land $ 0      
Original Building 0      
Costs Capitalized Subsequent to Acquisition 1,188,000      
Land held for development 1,188,000      
Total $ 1,188,000      
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] $ 4,276,609,000      
Original Cost        
Original Land 5,716,458,000      
Original Building 15,848,823,000      
Costs Capitalized Subsequent to Acquisition 6,589,630,000      
Land and Improvements [10] 5,908,096,000      
Building and Improvements [11] 20,768,125,000      
Land held for development [5] 714,050,000 [12] 697,061,000    
Development and Construction in Progress 764,640,000 547,280,000    
Total 28,154,911,000 27,055,206,000 25,376,700,000 23,734,833,000
Accumulated Depreciation 7,355,327,000 6,718,037,000 $ 6,143,384,000 $ 5,736,240,000
Furniture, Fixtures and Equipment 57,136,000 53,716,000    
Aggregate cost for tax purpose 28,900,000,000      
Real Estate Aggregate Accumulated Depreciation For Tax Purposes 7,100,000,000      
Debt Issuance Costs, Net (25,700,000)      
Right-of-use assets - finance leases [6] 372,922,000 401,680,000    
Operating Lease, Right-of-Use Asset [6] $ 334,767,000 $ 324,298,000    
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 $ 42,555,000      
Boston Properties Limited Partnership | Land and Land Improvements [Member]        
Original Cost        
Right-of-use assets - finance leases 349,314,000      
Operating Lease, Right-of-Use Asset 334,767,000      
Boston Properties Limited Partnership | Buildings and improvements        
Original Cost        
Right-of-use assets - finance leases 23,608,000      
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 2,291,498,000      
Original Cost        
Original Land 1,796,252,000      
Original Building 1,532,654,000      
Costs Capitalized Subsequent to Acquisition 393,520,000      
Land and Improvements 1,796,252,000      
Building and Improvements 1,926,174,000      
Total 3,722,426,000      
Accumulated Depreciation $ 567,621,000      
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 774,547,000      
Land and Improvements 100,533,000      
Building and Improvements 1,714,448,000      
Total 1,814,981,000      
Accumulated Depreciation $ 800,074,000      
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 507,972,000      
Land and Improvements 180,419,000      
Building and Improvements 1,354,660,000      
Total 1,535,079,000      
Accumulated Depreciation $ 806,969,000      
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 359,958,000      
Land and Improvements 339,200,000      
Building and Improvements 1,060,316,000      
Total 1,399,516,000      
Accumulated Depreciation $ 501,229,000      
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 $ 990,529,000      
Original Cost        
Original Land 241,600,000      
Original Building 494,782,000      
Costs Capitalized Subsequent to Acquisition 531,270,000      
Land and Improvements 279,281,000      
Building and Improvements 988,371,000      
Total 1,267,652,000      
Accumulated Depreciation $ 385,988,000      
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 288,694,000      
Land and Improvements 257,203,000      
Building and Improvements 918,918,000      
Total 1,176,121,000      
Accumulated Depreciation $ 370,980,000      
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 7,655,000      
Land and Improvements 200,349,000      
Building and Improvements 953,860,000      
Total 1,154,209,000      
Accumulated Depreciation $ 188,376,000      
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 51,331,000      
Land and Improvements 285,263,000      
Building and Improvements 654,498,000      
Total 939,761,000      
Accumulated Depreciation $ 215,386,000      
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 138,639,000      
Land and Improvements 131,067,000      
Building and Improvements 574,593,000      
Total 705,660,000      
Accumulated Depreciation $ 189,447,000      
Depreciable Lives (Years) [13] (1)      
Boston Properties Limited Partnership | 7 Times Square | Office and Life Sciences Building [Member]        
Original Cost        
Original Land $ 165,413,000      
Original Building 380,438,000      
Costs Capitalized Subsequent to Acquisition 112,011,000      
Land and Improvements 159,694,000      
Building and Improvements 498,168,000      
Total 657,862,000      
Accumulated Depreciation $ 250,824,000      
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 5,126,000      
Land and Improvements 104,641,000      
Building and Improvements 569,462,000      
Total 674,103,000      
Accumulated Depreciation $ 56,212,000      
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 169,851,000      
Land and Improvements 90,501,000      
Building and Improvements 479,895,000      
Land held for development 58,977,000      
Total 629,373,000      
Accumulated Depreciation $ 274,543,000      
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 $ 198,021,000      
Original Cost        
Original Land 46,360,000      
Original Building 410,421,000      
Costs Capitalized Subsequent to Acquisition 177,482,000      
Land and Improvements 210,471,000      
Building and Improvements 423,681,000      
Land held for development 111,000      
Total 634,263,000      
Accumulated Depreciation $ 18,660,000      
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 5,860,000      
Land and Improvements 2,901,000      
Building and Improvements 563,785,000      
Total 566,686,000      
Accumulated Depreciation $ 51,052,000      
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 42,166,000      
Land and Improvements 63,988,000      
Building and Improvements 496,703,000      
Total 560,691,000      
Accumulated Depreciation $ 195,192,000      
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 4,433,000      
Land and Improvements 185,203,000      
Building and Improvements 328,639,000      
Total 513,842,000      
Accumulated Depreciation $ 34,319,000      
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 242,168,000      
Land and Improvements 81,040,000      
Building and Improvements 342,675,000      
Total 423,715,000      
Accumulated Depreciation $ 202,504,000      
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 56,795,000      
Land and Improvements 56,853,000      
Building and Improvements 363,093,000      
Total 419,946,000      
Accumulated Depreciation $ 125,277,000      
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 37,287,000      
Land and Improvements 103,000,000      
Building and Improvements 290,952,000      
Total 393,952,000      
Accumulated Depreciation $ 111,209,000      
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 42,132,000      
Land and Improvements 21,403,000      
Building and Improvements 354,817,000      
Total 376,220,000      
Accumulated Depreciation $ 25,113,000      
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 12,577,000      
Land and Improvements 72,545,000      
Building and Improvements 232,343,000      
Total 304,888,000      
Accumulated Depreciation $ 87,930,000      
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 26,777,000      
Land and Improvements 23,164,000      
Building and Improvements 276,747,000      
Total 299,911,000      
Accumulated Depreciation $ 43,888,000      
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 116,540,000      
Land and Improvements 101,734,000      
Building and Improvements 198,347,000      
Total 300,081,000      
Accumulated Depreciation $ 75,450,000      
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 30,760,000      
Land and Improvements 13,603,000      
Building and Improvements 268,239,000      
Total 281,842,000      
Accumulated Depreciation $ 118,676,000      
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 95,025,000      
Land and Improvements 18,789,000      
Building and Improvements 238,765,000      
Land held for development 4,711,000      
Total 262,265,000      
Accumulated Depreciation $ 118,253,000      
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 6,325,000      
Land and Improvements 40,934,000      
Building and Improvements 154,702,000      
Total 195,636,000      
Accumulated Depreciation $ 50,973,000      
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 21,315,000      
Land and Improvements 95,066,000      
Building and Improvements 89,688,000      
Total 184,754,000      
Accumulated Depreciation $ 37,048,000      
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 51,754,000      
Land and Improvements 19,089,000      
Building and Improvements 155,394,000      
Total 174,483,000      
Accumulated Depreciation $ 90,370,000      
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 68,625,000      
Land and Improvements 18,095,000      
Building and Improvements 135,530,000      
Total 153,625,000      
Accumulated Depreciation $ 50,959,000      
Depreciable Lives (Years) [13] (1)      
Boston Properties Limited Partnership | 901 New York Avenue | Office and Life Sciences Building [Member]        
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances $ 201,692,000      
Original Cost        
Original Land 65,808,000      
Original Building 72,970,000      
Costs Capitalized Subsequent to Acquisition 13,225,000      
Land and Improvements 65,808,000      
Building and Improvements 86,195,000      
Total 152,003,000      
Accumulated Depreciation $ 4,253,000      
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 35,160,000      
Land and Improvements 25,982,000      
Building and Improvements 117,471,000      
Total 143,453,000      
Accumulated Depreciation $ 57,126,000      
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 41,943,000      
Land and Improvements 9,883,000      
Building and Improvements 126,493,000      
Total 136,376,000      
Accumulated Depreciation $ 71,339,000      
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 40,024,000      
Land and Improvements 13,866,000      
Building and Improvements 117,827,000      
Total 131,693,000      
Accumulated Depreciation $ 48,454,000      
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 45,178,000      
Land and Improvements 15,074,000      
Building and Improvements 112,752,000      
Total 127,826,000      
Accumulated Depreciation $ 62,667,000      
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 4,132,000      
Land and Improvements 18,021,000      
Building and Improvements 113,170,000      
Total 131,191,000      
Accumulated Depreciation $ 57,705,000      
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 1,630,000      
Land and Improvements 25,854,000      
Building and Improvements 93,841,000      
Total 119,695,000      
Accumulated Depreciation $ 44,575,000      
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 28,359,000      
Land and Improvements 11,146,000      
Building and Improvements 100,193,000      
Total 111,339,000      
Accumulated Depreciation $ 60,237,000      
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 (284,000)      
Land and Improvements 26,834,000      
Building and Improvements 35,014,000      
Land held for development 54,110,000      
Total 115,958,000      
Accumulated Depreciation $ 5,526,000      
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 $ 594,869,000      
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 $ 39,544,000      
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 $ 21,016,000      
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 6,862,000      
Land and Improvements 2,127,000      
Building and Improvements 92,440,000      
Total 94,567,000      
Accumulated Depreciation $ 26,693,000      
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 19,758,000      
Land and Improvements 10,350,000      
Building and Improvements 80,487,000      
Total 90,837,000      
Accumulated Depreciation $ 47,541,000      
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 21,989,000      
Land and Improvements 20,741,000      
Building and Improvements 72,430,000      
Total 93,171,000      
Accumulated Depreciation $ 33,338,000      
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 58,886,000      
Land and Improvements 26,921,000      
Building and Improvements 61,334,000      
Total 88,255,000      
Accumulated Depreciation $ 28,998,000      
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 23,458,000      
Land and Improvements 13,403,000      
Building and Improvements 73,067,000      
Total 86,470,000      
Accumulated Depreciation $ 41,224,000      
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 10,543,000      
Land and Improvements 13,997,000      
Building and Improvements 70,776,000      
Total 84,773,000      
Accumulated Depreciation $ 30,716,000      
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 $ 16,456,000      
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 26,100,000      
Land and Improvements 0      
Building and Improvements 79,449,000      
Total 79,449,000      
Accumulated Depreciation $ 31,223,000      
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 $ 23,427,000      
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 $ 34,685,000      
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 19,104,000      
Land and Improvements 13,913,000      
Building and Improvements 47,661,000      
Total 61,574,000      
Accumulated Depreciation $ 9,397,000      
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 32,110,000      
Land and Improvements 134,000      
Building and Improvements 57,220,000      
Total 57,354,000      
Accumulated Depreciation $ 45,229,000      
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 13,699,000      
Land and Improvements 4,145,000      
Building and Improvements 46,645,000      
Total 50,790,000      
Accumulated Depreciation $ 37,845,000      
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 5,712,000      
Land and Improvements 6,128,000      
Building and Improvements 33,874,000      
Total 40,002,000      
Accumulated Depreciation $ 24,060,000      
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 6,093,000      
Land and Improvements 23,372,000      
Building and Improvements 19,188,000      
Total 42,560,000      
Accumulated Depreciation $ 17,845,000      
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 $ 19,464,000      
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 $ 17,361,000      
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 18,974,000      
Land and Improvements 1,072,000      
Building and Improvements 18,660,000      
Land held for development 1,666,000      
Total 21,398,000      
Accumulated Depreciation $ 17,028,000      
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 $ 2,969,000      
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 $ 4,723,000      
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 $ 3,885,000      
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 9,049,000      
Land and Improvements 26,000      
Building and Improvements 6,057,000      
Land held for development 3,142,000      
Total 9,225,000      
Accumulated Depreciation $ 3,774,000      
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 5,808,000      
Land and Improvements 168,000      
Building and Improvements 7,751,000      
Total 7,919,000      
Accumulated Depreciation $ 3,080,000      
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 $ 1,300,000      
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 5,580,000      
Land and Improvements 126,364,000      
Building and Improvements 439,242,000      
Total 565,606,000      
Accumulated Depreciation $ 38,051,000      
Depreciable Lives (Years) [13] (1)      
Boston Properties Limited Partnership | 180 CityPoint [Member] | Office and Life Sciences Building [Member]        
Original Cost        
Original Land $ 10,908,000      
Original Building 211,883,000      
Costs Capitalized Subsequent to Acquisition 0      
Land and Improvements 10,908,000      
Building and Improvements 211,883,000      
Total 222,791,000      
Accumulated Depreciation $ 6,212,000      
Depreciable Lives (Years) (1)      
Boston Properties Limited Partnership | 300 Binney Street | Office and Life Sciences Building [Member]        
Original Cost        
Original Land $ 18,080,000      
Original Building 51,262,000      
Costs Capitalized Subsequent to Acquisition 148,974,000      
Land and Improvements 18,080,000      
Building and Improvements 200,236,000      
Total 218,316,000      
Accumulated Depreciation $ 7,923,000      
Depreciable Lives (Years) (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 95,615,000      
Land and Improvements 15,597,000      
Building and Improvements 132,870,000      
Total 148,467,000      
Accumulated Depreciation $ 18,179,000      
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 75,048,000      
Land and Improvements 16,148,000      
Building and Improvements 99,674,000      
Land held for development 357,000      
Total 116,179,000      
Accumulated Depreciation $ 32,778,000      
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 2,352,000      
Land and Improvements 33,233,000      
Building and Improvements 58,292,000      
Total 91,525,000      
Accumulated Depreciation $ 7,583,000      
Depreciable Lives (Years) [13] (1)      
Boston Properties Limited Partnership | 103 CityPoint | Office and Life Sciences Building [Member]        
Original Cost        
Original Land $ 4,672,000      
Original Building 77,515,000      
Costs Capitalized Subsequent to Acquisition (2,000)      
Land and Improvements 4,670,000      
Building and Improvements 77,515,000      
Total 82,185,000      
Accumulated Depreciation $ 569,000      
Depreciable Lives (Years) (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 $ 7,243,000      
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 $ 10,022,000      
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 1,088,000      
Land and Improvements 595,000      
Building and Improvements 7,835,000      
Total 8,430,000      
Accumulated Depreciation $ 7,194,000      
Depreciable Lives (Years) [13] (1)      
Boston Properties Limited Partnership | The Skylyne | Residential Building        
Original Cost        
Original Land $ 0      
Original Building 239,077,000      
Costs Capitalized Subsequent to Acquisition 1,792,000      
Building and Improvements 240,869,000      
Total 240,869,000      
Accumulated Depreciation $ 26,207,000      
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 2,980,000      
Land and Improvements 27,076,000      
Building and Improvements 193,560,000      
Total 220,636,000      
Accumulated Depreciation $ 32,887,000      
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 $ 21,122,000      
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 2,598,000      
Land and Improvements 3,529,000      
Building and Improvements 57,489,000      
Total 61,018,000      
Accumulated Depreciation $ 20,108,000      
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 27,140,000      
Land and Improvements 478,000      
Building and Improvements 64,429,000      
Land held for development 629,000      
Total 65,536,000      
Accumulated Depreciation $ 52,309,000      
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 $ 19,665,000      
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 962,000      
Land and Improvements 1,256,000      
Building and Improvements 16,659,000      
Total 17,915,000      
Accumulated Depreciation $ 7,997,000      
Depreciable Lives (Years) [13] (1)      
Boston Properties Limited Partnership | 290 Binney Street | Development        
Original Cost        
Original Land $ 0      
Original Building 0      
Costs Capitalized Subsequent to Acquisition 575,542,000      
Land and Improvements 638,000      
Development and Construction in Progress 574,904,000      
Total 575,542,000      
Accumulated Depreciation $ 0      
Depreciable Lives (Years) N/A      
Boston Properties Limited Partnership | 121 Broadway | Development        
Original Cost        
Original Land $ 0      
Original Building 0      
Costs Capitalized Subsequent to Acquisition 102,843,000      
Development and Construction in Progress 102,843,000      
Total 102,843,000      
Accumulated Depreciation $ 0      
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 45,434,000      
Land and Improvements 1,692,000      
Building and Improvements 3,030,000      
Development and Construction in Progress 40,712,000      
Total 45,434,000      
Accumulated Depreciation $ 14,000      
Depreciable Lives (Years) N/A      
Boston Properties Limited Partnership | 725 12th Street | Development        
Original Cost        
Original Land $ 26,997,000      
Original Building 8,369,000      
Costs Capitalized Subsequent to Acquisition 522,000      
Development and Construction in Progress 35,888,000      
Total 35,888,000      
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 10,293,000      
Development and Construction in Progress 10,293,000      
Total 10,293,000      
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 240,226,000      
Land and Improvements 140,558,000      
Land held for development 99,668,000      
Total 240,226,000      
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 28,366,000      
Building and Improvements 47,000      
Land held for development 172,966,000      
Total 173,013,000      
Accumulated Depreciation $ 39,000      
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 103,908,000      
Land and Improvements 24,808,000      
Land held for development 79,100,000      
Total 103,908,000      
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 5,185,000      
Land held for development 68,391,000      
Total 68,391,000      
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 4,600,000      
Land held for development 39,604,000      
Total 39,604,000      
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 36,522,000      
Land held for development 36,522,000      
Total 36,522,000      
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 19,913,000      
Land held for development 19,913,000      
Total 19,913,000      
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 17,199,000      
Land held for development 17,199,000      
Total 17,199,000      
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 16,301,000      
Land held for development 16,301,000      
Total 16,301,000      
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 1,252,000      
Land held for development 1,252,000      
Total 1,252,000      
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 1,188,000      
Land held for development 1,188,000      
Total 1,188,000      
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 $(25.7) million.
[2] Includes Right of Use Assets - Finance Leases and Right of Use Assets - Operating Leases of approximately $349,314 and $334,767, respectively.
[3] Includes Right of Use Assets - Finance Leases of approximately $23,608.
[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.
[9] Includes unamortized deferred financing costs and fair value debt adjustment totaling approximately $(25.7) million.
[10] Includes Right of Use Assets - Finance Leases and Right of Use Assets - Operating Leases of approximately $349,314 and $334,767, respectively.
[11] Includes Right of Use Assets - Finance Leases of approximately $23,608.
[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.