Investments in Unconsolidated Joint Ventures (Statements of Operations of the Joint Ventures) (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2023		Sep. 30, 2022	Sep. 30, 2023		Sep. 30, 2022
Schedule of Equity Method Investments [Line Items]
Total revenue		$ 824,283		$ 790,523	$ 2,444,636		$ 2,318,757
Expenses
Transaction costs		751		1,650	1,970		2,146
Depreciation and amortization		207,435		190,675	618,746		551,445
Total expenses		552,714		518,994	1,672,241		1,520,810
Other income (expense)
Interest expense		(147,812)		(111,846)	(424,492)		(317,216)
Gains on sales of real estate		517		262,345	517		381,293
Net Loss		(103,543)		420,661	138,269		864,861
Income (Loss) from Equity Method Investments		(247,556)		(3,524)	(261,793)		(1,389)
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Total revenue	[1]	153,551		127,996	469,745		373,358
Expenses
Operating		65,119		52,886	183,348		143,880
Transaction costs		78		(65)	179		746
Depreciation and amortization		49,840		44,132	151,051		132,089
Total expenses		115,037		96,953	334,578		276,715
Other income (expense)
Losses from early extinguishment of debt		0		0	(3)		(1,327)
Interest expense		(60,737)		(40,678)	(176,786)		(103,270)
Unrealized gain on derivative instruments		10,242		0	(14,089)		0
Net Loss		(11,981)		(9,635)	(27,533)		(7,954)
Company's share of net income (loss)		(4,476)		(2,251)	(10,739)		2,225
Gain on Unconsolidated Joint Venture Investment		35,756	[2]	0	35,756	[2]	0
Impairment loss on investment		(272,603)	[3]	0	(272,603)	[3]	0
Basis differential	[4]	(6,233)		(1,273)	(14,207)		(3,614)
Income (Loss) from Equity Method Investments		(247,556)		(3,524)	(261,793)		(1,389)
Straight Line Rent Adjustments		7,700		9,600	20,900		54,900
Above and below market rent adjustments, net		200		100	600		300
Colorado Center [Member] | Unconsolidated Joint Ventures [Member]
Other income (expense)
Straight Line Rent Adjustments		400		$ 100	$ 1,100		$ 300
200 Fifth Avenue JV LLC
Other income (expense)
Impairment loss on investment		(33,400)
Safeco Plaza REIT LLC
Other income (expense)
Impairment loss on investment		(29,900)
Platform 16
Other income (expense)
Impairment loss on investment		(155,200)
360 PAS Holdco LLC
Other income (expense)
Impairment loss on investment		$ (54,000)

[1] Includes straight-line rent adjustments of approximately $7.7 million and $9.6 million for the three months ended September 30, 2023 and 2022, respectively, and approximately $20.9 million and $54.9 million for the nine months ended September 30, 2023 and 2022, respectively.

[2] During the three months ended September 30, 2023, the Company completed a restructuring of its ownership in Metropolitan Square, as described below in this Note 5.

[3] During the three months ended September 30, 2023, the Company recognized an other-than-temporary impairment loss on its investments in Platform 16, 360 Park Avenue South, 200 Fifth Avenue and Safeco Plaza of approximately $155.2 million, $54.0 million, $33.4 million and $29.9 million respectively, as described below in this Note 5.

[4] Includes straight-line rent adjustments of approximately $0.4 million and $0.1 million for the three months ended September 30, 2023 and 2022, respectively, and approximately $1.1 million and $0.3 million for the nine months ended September 30, 2023 and 2022, respectively. Also includes net above-/below-market rent adjustments of approximately $0.2 million and $0.1 million for the three months ended September 30, 2023 and 2022, respectively, and approximately $0.6 million and $0.3 million for the nine months ended September 30, 2023 and 2022.