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Segment Information (Schedule Of Reconciliation Of Net Operating Income To Net Income) (Details) - USD ($) | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |  |
Net income attributable to the Company's common shareholders / unitholders | $ 862,227,000 | $ 511,034,000 |  | $ 572,347,000 |
Preferred dividends / distributions | (10,500,000) | (10,500,000) |  | (10,500,000) |
Noncontrolling interest-common units of the Operating Partnership | (97,704,000) | (59,345,000) |  | (66,807,000) |
Noncontrolling interest in property partnerships | (48,260,000) | (71,120,000) |  | (62,909,000) |
Interest expense | (431,717,000) | (412,717,000) |  | (378,168,000) |
Loss from early extinguishment of debt | 0 | 29,540,000 |  | 16,490,000 |
Company's share of net operating income from joint ventures | (1,694,075,000) | (1,826,123,000) |  | (1,649,314,000) |
Depreciation and amortization expense | (683,751,000) | (677,764,000) |  | (645,649,000) |
Transaction costs | (1,531,000) | (1,984,000) |  | (1,604,000) |
General and administrative expense | (133,112,000) | (140,777,000) |  | (121,722,000) |
Gains (losses) from investments in securities | (5,261,000) | (6,417,000) |  | 1,865,000 |
Interest and other income (loss) | (5,953,000) | (18,939,000) |  | (10,823,000) |
Gains on sales of real estate | (618,982,000) | (709,000) |  | (182,356,000) |
Income (loss) from unconsolidated joint ventures | 85,110,000 | (46,592,000) |  | (2,222,000) |
Business Intersegment, Eliminations [Member] |  |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |  |
Net income attributable to the Company's common shareholders / unitholders | 862,227,000 | 511,034,000 |  | 572,347,000 |
Preferred dividends / distributions | 10,500,000 | 10,500,000 |  | 10,500,000 |
Noncontrolling interest-common units of the Operating Partnership | 97,704,000 | 59,345,000 |  | 66,807,000 |
Noncontrolling interest in property partnerships | 48,260,000 | 71,120,000 |  | 62,909,000 |
Interest expense | 431,717,000 | 412,717,000 |  | 378,168,000 |
Loss from early extinguishment of debt | 0 | 29,540,000 |  | 16,490,000 |
Impairment loss | 0 | 24,038,000 |  | 11,812,000 |
Depreciation and amortization expense | 683,751,000 | 677,764,000 |  | 645,649,000 |
Transaction costs | 1,531,000 | 1,984,000 |  | 1,604,000 |
Operating expense | 11,626,000 | 10,386,000 |  | 9,590,000 |
General and administrative expense | 133,112,000 | 140,777,000 |  | 121,722,000 |
Gains (losses) from investments in securities | 5,261,000 | 6,417,000 |  | (1,865,000) |
Interest and other income (loss) | 5,953,000 | 18,939,000 |  | 10,823,000 |
Gains on sales of real estate | 618,982,000 | 709,000 |  | 182,356,000 |
Income (loss) from unconsolidated joint ventures | (85,110,000) | 46,592,000 |  | 2,222,000 |
Other revenue | 11,626,000 | 10,386,000 |  | 9,590,000 |
Company's share of Net Operating Income | 1,626,131,000 | 1,739,850,000 |  | 1,551,842,000 |
Unconsolidated Joint Ventures [Member] |  |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |  |
Interest expense | (98,051,000) | (84,409,000) |  | (71,308,000) |
Company's share of net operating income from joint ventures | (94,943,000) | (97,716,000) |  | (79,893,000) |
Depreciation and amortization expense | (141,853,000) | (102,296,000) |  | (103,079,000) | [1]
Transaction costs | (1,027,000) | (1,000,000) |  | 0 |
Gains on sales of real estate | (11,737,000) | (32,706,000) | [2] | (16,951,000) |
Income (loss) from unconsolidated joint ventures | 85,110,000 | (46,592,000) |  | (2,222,000) |
Unconsolidated Joint Ventures [Member] | Business Intersegment, Eliminations [Member] |  |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |  |
Company's share of net operating income from joint ventures | 94,943,000 | 97,716,000 |  | 79,893,000 |
Boston Properties Limited Partnership |  |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |  |
Net income attributable to the Company's common shareholders / unitholders | 979,979,000 | 580,102,000 |  | 656,903,000 |
Preferred dividends / distributions | (10,500,000) | (10,500,000) |  | (10,500,000) |
Noncontrolling interest in property partnerships | (48,260,000) | (71,120,000) |  | (62,909,000) |
Interest expense | (431,717,000) | (412,717,000) |  | (378,168,000) |
Loss from early extinguishment of debt | 0 | 29,540,000 |  | 16,490,000 |
Depreciation and amortization expense | (676,666,000) | (669,956,000) |  |  |
Transaction costs | (1,531,000) | (1,984,000) |  | (1,604,000) |
General and administrative expense | (133,112,000) | (140,777,000) |  | (121,722,000) |
Gains (losses) from investments in securities | (5,261,000) | (6,417,000) |  | 1,865,000 |
Interest and other income (loss) | (5,953,000) | (18,939,000) |  | (10,823,000) |
Gains on sales of real estate | (631,945,000) | (858,000) |  | (190,716,000) |
Income (loss) from unconsolidated joint ventures | 85,110,000 | (46,592,000) |  | (2,222,000) |
Boston Properties Limited Partnership | Business Intersegment, Eliminations [Member] |  |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |  |
Net income attributable to the Company's common shareholders / unitholders | 979,979,000 | 580,102,000 |  | 656,903,000 |
Preferred dividends / distributions | 10,500,000 | 10,500,000 |  | 10,500,000 |
Noncontrolling interest in property partnerships | 48,260,000 | 71,120,000 |  | 62,909,000 |
Interest expense | 431,717,000 | 412,717,000 |  | 378,168,000 |
Loss from early extinguishment of debt | 0 | 29,540,000 |  | 16,490,000 |
Impairment loss | 0 | 22,272,000 |  | 10,181,000 |
Depreciation and amortization expense | 676,666,000 | 669,956,000 |  | 637,891,000 |
Transaction costs | 1,531,000 | 1,984,000 |  | 1,604,000 |
Operating expense | 11,626,000 | 10,386,000 |  | 9,590,000 |
General and administrative expense | 133,112,000 | 140,777,000 |  | 121,722,000 |
Gains (losses) from investments in securities | 5,261,000 | 6,417,000 |  | (1,865,000) |
Interest and other income (loss) | 5,953,000 | 18,939,000 |  | 10,823,000 |
Gains on sales of real estate | 631,945,000 | 858,000 |  | 190,716,000 |
Income (loss) from unconsolidated joint ventures | (85,110,000) | 46,592,000 |  | 2,222,000 |
Other revenue | 11,626,000 | 10,386,000 |  | 9,590,000 |
Company's share of Net Operating Income | 1,626,131,000 | 1,739,850,000 |  | 1,551,842,000 |
Management Service [Member] |  |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |  |
Other revenue | (29,641,000) | (40,039,000) |  | (45,158,000) |
Management Service [Member] | Business Intersegment, Eliminations [Member] |  |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |  |
Other revenue | 29,641,000 | 40,039,000 |  | 45,158,000 |
Management Service [Member] | Boston Properties Limited Partnership |  |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |  |
Other revenue | (29,641,000) | (40,039,000) |  | (45,158,000) |
Management Service [Member] | Boston Properties Limited Partnership | Business Intersegment, Eliminations [Member] |  |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |  |
Other revenue | 29,641,000 | 40,039,000 |  | 45,158,000 |
Noncontrolling interest - property partnerships [Member] |  |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |  |
Company's share of net operating income from joint ventures | 162,887,000 | 183,989,000 |  | 177,365,000 |
Noncontrolling interest - property partnerships [Member] | Business Intersegment, Eliminations [Member] |  |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |  |
Company's share of net operating income from joint ventures | 162,887,000 | 183,989,000 |  | 177,365,000 |
Noncontrolling interest - property partnerships [Member] | Boston Properties Limited Partnership | Business Intersegment, Eliminations [Member] |  |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |  |
Company's share of net operating income from joint ventures | $ 162,887,000 | $ 183,989,000 |  | $ 177,365,000 |
[1] | During the year ended December 31, 2018, the joint venture that owns Metropolitan Square in Washington, DC, commenced a renovation project and recorded accelerated depreciation expense of approximately $22.4 million related to the remaining book value of the assets to be replaced. The Company’s share of the accelerated depreciation expense totaled approximately $4.5 million.
[2] | For the year ended December 31, 2019, represents the gain on sale of 540 Madison Avenue recognized by the joint venture. During 2008, the Company recognized an other-than-temporary impairment loss on its investment in the unconsolidated joint venture resulting in a basis differential between the carrying value of the Company’s investment in the joint venture and the joint venture’s basis in the assets and liabilities of the property. As a result of the historical basis difference, the Company recognized a gain on sale of real estate totaling approximately $47.2 million for the year ended December 31, 2019, which consists of its share of the gain on sale reported by the joint venture as well as an adjustment for the basis differential. The gain on sale of real estate is included in Income from Unconsolidated Joint Ventures in the Company’s Consolidated Statements of Operations.

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