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Investments in Unconsolidated Joint Ventures (Statements of Operations of the Joint Ventures) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Total revenue |  | $ 2,765,686 |  | $ 2,960,562 |  | $ 2,717,076 |
Expenses |  |  |  |  |  |  |
Transaction costs |  | 1,531 |  | 1,984 |  | 1,604 |
Depreciation and amortization |  | 683,751 |  | 677,764 |  | 645,649 |
Total expenses |  | 1,860,364 |  | 1,914,925 |  | 1,791,579 |
Other income (expense) |  |  |  |  |  |  |
Interest expense |  | (431,717) |  | (412,717) |  | (378,168) |
Gains on sales of real estate |  | 618,982 |  | 709 |  | 182,356 |
Net income |  | 1,018,691 |  | 651,999 |  | 712,563 |
Income (Loss) from Equity Method Investments |  | (85,110) |  | 46,592 |  | 2,222 |
Straight-line rent adjustments |  | (104,900) |  | (58,400) |  | (51,900) |
Above and below market rent adjustments, net |  | 6,500 |  | 20,900 |  | 23,800 |
Write-off for accrued rent |  | 67,700 |  |  |  |  |
Unconsolidated Joint Ventures [Member] |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Total revenue | [1] | 319,560 |  | 322,817 |  | 271,951 |
Expenses |  |  |  |  |  |  |
Operating |  | 144,347 |  | 122,992 |  | 106,610 |
Transaction costs |  | 1,027 |  | 1,000 |  | 0 |
Depreciation and amortization |  | 141,853 |  | 102,296 |  | 103,079 | [2]
Total expenses |  | 287,227 |  | 226,288 |  | 209,689 |
Other income (expense) |  |  |  |  |  |  |
Interest expense |  | (98,051) |  | (84,409) |  | (71,308) |
Gains on sales of real estate |  | 11,737 |  | 32,706 | [3] | 16,951 |
Net income |  | (53,981) |  | 44,826 |  | 7,905 |
Company's share of net income |  | (16,256) |  | 24,423 |  | 8,084 |
Impairment loss on investment |  | (60,524) | [4] | 0 |  | 0 |
Basis differential | [5] | (8,330) | [4] | 22,169 | [3] | (5,862) |
Income (Loss) from Equity Method Investments |  | (85,110) |  | 46,592 |  | 2,222 |
Straight-line rent adjustments |  | (10,100) |  | 32,400 |  | 15,900 |
Write-off for accrued rent |  | 51,700 |  |  |  |  |
Colorado Center [Member] |  |  |  |  |  |  |
Other income (expense) |  |  |  |  |  |  |
Straight-line rent adjustments |  | 1,800 |  | 2,100 |  | 2,400 |
Above and below market rent adjustments, net |  | 900 |  | 1,700 |  | 1,600 |
Dock 72 [Member] |  |  |  |  |  |  |
Other income (expense) |  |  |  |  |  |  |
Impairment loss on investment |  | $ (60,500) |  |  |  |  |
540 Madison Avenue [Member] |  |  |  |  |  |  |
Other income (expense) |  |  |  |  |  |  |
Gains on sales of real estate |  |  |  | $ 47,200 |  |  |
Metropolitan Square |  |  |  |  |  |  |
Expenses |  |  |  |  |  |  |
Depreciation and amortization |  |  |  |  |  | 22,400 |
Metropolitan Square | Company's Share [Member] |  |  |  |  |  |  |
Expenses |  |  |  |  |  |  |
Depreciation and amortization |  |  |  |  |  | $ 4,500 |
[1] | Includes straight-line rent adjustments of approximately $(10.1) million, $32.4 million and $15.9 million for the years ended December 31, 2020, 2019 and 2018, respectively. Due primarily to the impact of COVID-19, for the year ended December 31, 2020, write-offs of accounts receivable and accrued rent balances totaled approximately $51.7 million.
[2] | 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.
[3] | 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.
[4] | During the year ended December 31, 2020, the Company recognized an other-than-temporary impairment loss on its investment in the unconsolidated joint venture that owns Dock 72 in Brooklyn, New York totaling approximately $60.5 million.
[5] | Includes straight-line rent adjustments of approximately $1.8 million, $2.1 million and $2.4 million for the years ended December 31, 2020, 2019 and 2018, respectively. Also includes net above-/below-market rent adjustments of approximately $0.9 million, $1.7 million and $1.6 million for the years ended December 31, 2020, 2019 and 2018, respectively.

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