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Investments in Unconsolidated Joint Ventures (Balance Sheets of the Unconsolidated Joint Ventures) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024 | Dec. 31, 2024
ASSETS |  |  |  |  |  |  |  |
Total real estate |  | $ 21,294,686 |  |  | $ 21,294,686 |  |  | $ 21,050,255
Total assets |  | 25,999,482 |  |  | 25,999,482 |  |  | 26,084,980
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY |  |  |  |  |  |  |  |
Mortgage and notes payable, net |  | 4,279,482 |  |  | 4,279,482 |  |  | 4,276,609
Other Liabilities |  | 406,820 |  |  | 406,820 |  |  | 450,796
Members’/Partners’ equity |  | 4,999,559 |  |  | 4,999,559 |  |  | 5,413,306
Total liabilities and equity / capital |  | 25,999,482 |  |  | 25,999,482 |  |  | 26,084,980
Carying value of the Company's investment in unconsolidated joint ventures |  | 999,764 |  |  | 999,764 |  |  | 1,093,583
Operating Lease, Right-of-Use Asset |  | 321,063 |  |  | 321,063 |  |  | 334,767
Lease Liabilities - Operating Leases |  | 379,792 |  |  | 379,792 |  |  | 392,686
Unconsolidated Joint Ventures [Member] |  |  |  |  |  |  |  |
ASSETS |  |  |  |  |  |  |  |
Total real estate | [1] | 5,781,519 |  |  | 5,781,519 |  |  | 5,748,198
Other assets | [2] | 708,615 |  |  | 708,615 |  |  | 703,096
Total assets |  | 6,490,134 |  |  | 6,490,134 |  |  | 6,451,294
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY |  |  |  |  |  |  |  |
Mortgage and notes payable, net |  | 3,186,295 |  |  | 3,186,295 |  |  | 3,206,723
Other Liabilities | [3] | 252,689 |  |  | 252,689 |  |  | 292,125
Members’/Partners’ equity |  | 3,051,150 |  |  | 3,051,150 |  |  | 2,952,446
Total liabilities and equity / capital |  | 6,490,134 |  |  | 6,490,134 |  |  | 6,451,294
Company's share of equity |  | 1,365,565 |  |  | 1,365,565 |  |  | 1,344,543
Basis differentials | [4] | (416,253) |  |  | (416,253) |  |  | (284,469)
Carying value of the Company's investment in unconsolidated joint ventures | [5] | 949,312 |  |  | 949,312 |  |  | 1,060,074
Operating Lease, Right-of-Use Asset |  | 18,100 |  |  | 18,100 |  |  | 19,000
Sales-type lease receivable, net |  | 14,300 |  |  | 14,300 |  |  | 14,100
Lease Liabilities - Operating Leases |  | 30,500 |  |  | 30,500 |  |  | 30,500
Equity Method Investment, Other-than-Temporary Impairment |  | 145,133 | [6] | $ 0 | 145,133 | [6] | $ 0 |
Unconsolidated Joint Ventures [Member] |  |  |  |  |  |  |  |
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY |  |  |  |  |  |  |  |
Other Liabilities |  | 50,500 |  |  | 50,500 |  |  | 33,500
Colorado Center |  |  |  |  |  |  |  |
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY |  |  |  |  |  |  |  |
Basis differentials |  | 130,440 |  |  | 130,440 |  |  | 127,632
Carying value of the Company's investment in unconsolidated joint ventures | [7] | 69,015 |  |  | 69,015 |  |  | 65,000
Equity Method Investment, Other-than-Temporary Impairment |  |  |  |  |  |  |  | 168,400
200 Fifth Avenue JV LLC |  |  |  |  |  |  |  |
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY |  |  |  |  |  |  |  |
Basis differentials |  | 48,864 |  |  | 48,864 |  |  | 49,656
Carying value of the Company's investment in unconsolidated joint ventures | [7] | 75,376 |  |  | 75,376 |  |  | 70,673
Gateway Commons Complex [Member] |  |  |  |  |  |  |  |
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY |  |  |  |  |  |  |  |
Basis differentials |  | (216,170) |  |  | (216,170) |  |  | (74,500)
Carying value of the Company's investment in unconsolidated joint ventures | [7] | 125,090 |  |  | 125,090 |  |  | 272,000
Equity Method Investment, Other-than-Temporary Impairment |  | 145,100 |  |  | 145,100 |  |  | 126,100
Safeco Plaza REIT LLC |  |  |  |  |  |  |  |
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY |  |  |  |  |  |  |  |
Basis differentials |  | (73,275) |  |  | (73,275) |  |  | (75,576)
Carying value of the Company's investment in unconsolidated joint ventures | [7] | 121 |  |  | 121 |  |  | 0
Equity Method Investment, Other-than-Temporary Impairment |  |  |  |  |  |  |  | 46,800
Dock 72 |  |  |  |  |  |  |  |
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY |  |  |  |  |  |  |  |
Other Liabilities | [7] | 14,326 |  |  | 14,326 |  |  | 9,889
Basis differentials |  | (89,347) |  |  | (89,347) |  |  | (92,054)
360 Park Avenue South |  |  |  |  |  |  |  |
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY |  |  |  |  |  |  |  |
Basis differentials |  | (111,025) |  |  | (111,025) |  |  | (113,265)
Carying value of the Company's investment in unconsolidated joint ventures | [7] | 93,988 |  |  | 93,988 |  |  | 74,592
Platform 16 |  |  |  |  |  |  |  |
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY |  |  |  |  |  |  |  |
Basis differentials |  | (142,666) |  |  | (142,666) |  |  | (142,698)
Carying value of the Company's investment in unconsolidated joint ventures | [7] | 58,076 |  |  | 58,076 |  |  | 56,265
Remaining Other Investment |  |  |  |  |  |  |  |
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY |  |  |  |  |  |  |  |
Basis differentials |  | $ 36,926 |  |  | $ 36,926 |  |  | $ 36,336
[1] | At September 30, 2025 and December 31, 2024, this amount included right of use assets - operating leases totaling approximately $18.1 million and $19.0 million, respectively.
[2] | At September 30, 2025 and December 31, 2024, this amount included sales-type lease receivable, net totaling approximately $14.3 million and $14.1 million, respectively.
[3] | At September 30, 2025 and December 31, 2024, this amount included lease liabilities - operating leases totaling approximately $30.5 million.
[4] | This amount represents the aggregate difference between the Company’s historical cost basis and the basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials result from impairments of investments, acquisitions through joint ventures with no change in control and upon the transfer of assets that were previously owned by the Company into a joint venture. During the thee months ended September 30, 2025, the Company recognized an other-than-temporary impairment loss on its investment in Gateway Commons of approximately $145.1 million. During the year ended December 31, 2024, the Company recognized an other-than-temporary impairment loss on its investments in Colorado Center, Gateway Commons and Safeco Plaza of approximately $168.4 million, $126.1 million, and $46.8 million, respectively. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the joint venture level. The Company’s basis differences include:
| September 30, 2025 |  | December 31, 2024
Property | (in thousands)
Colorado Center | $ | 130,440 |  |  | $ | 127,632 |
200 Fifth Avenue | 48,864 |  |  | 49,656 |
Gateway Commons | (216,170) |  |  | (74,500) |
Safeco Plaza | (73,275) |  |  | (75,576) |
Dock 72 | (89,347) |  |  | (92,054) |
360 Park Avenue South | (111,025) |  |  | (113,265) |
Platform 16 | (142,666) |  |  | (142,698) |
Other basis differentials | 36,926 |  |  | 36,336 |
Total basis differentials | $ | (416,253) |  |  | $ | (284,469) |
These basis differentials (excluding land) will be amortized over the remaining lives of the related assets and liabilities.
[5] | Investments with deficit balances aggregating approximately $50.5 million and $33.5 million at September 30, 2025 and December 31, 2024, respectively, are reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.
[6] | During the three and nine months ended September 30, 2025, the Company recognized an other-than-temporary impairment loss on its investment in Gateway Commons of approximately $145.1 million.
[7] | Investments with deficit balances aggregating approximately $50.5 million and $33.5 million at September 30, 2025 and December 31, 2024, respectively, are included within Other Liabilities in the Company’s Consolidated Balance Sheets.

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