Segment Information (Summary of NOI by Segment) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total revenues	$ 460,968	$ 465,961	$ 463,103	$ 534,668	$ 543,417	$ 542,048	$ 541,818	$ 536,437	$ 1,924,700	$ 2,163,720	$ 2,084,126
Operating expenses									(917,981)	(963,478)	(886,596)
NOI - consolidated									1,006,719	1,200,242	1,197,530
Deduct: NOI attributable to noncontrolling interests in consolidated subsidiaries									(69,332)	(71,186)	(65,311)
Add: Our share of NOI from partially owned entities									322,390	253,564	269,164
NOI at share									1,259,777	1,382,620	1,401,383
Non-cash adjustments for straight-line rents, amortization of acquired below-market leases, net and other									(6,060)	(44,704)	(86,842)
NOI at share - cash basis									1,253,717	1,337,916	1,314,541
Balance Sheet Data:
Real estate, at cost	13,074,012				16,237,883				13,074,012	16,237,883	14,756,295	$ 14,187,820
Investments in partially owned entities	3,999,165				858,113				3,999,165	858,113
Assets	18,287,013				17,180,794				18,287,013	17,180,794
New York
Segment Reporting Information [Line Items]
Total revenues									1,577,860	1,836,036	1,779,307
Operating expenses									(758,304)	(806,464)	(756,670)
NOI - consolidated									819,556	1,029,572	1,022,637
Deduct: NOI attributable to noncontrolling interests in consolidated subsidiaries									(40,896)	(48,490)	(45,899)
Add: Our share of NOI from partially owned entities									294,168	195,908	189,327
NOI at share									1,072,828	1,176,990	1,166,065
Non-cash adjustments for straight-line rents, amortization of acquired below-market leases, net and other									(12,318)	(45,427)	(79,202)
NOI at share - cash basis									1,060,510	1,131,563	1,086,863
Balance Sheet Data:
Real estate, at cost	10,272,458				12,351,943				10,272,458	12,351,943
Investments in partially owned entities	3,964,289				719,456				3,964,289	719,456
Assets	16,429,159				14,628,712				16,429,159	14,628,712
Other
Segment Reporting Information [Line Items]
Total revenues									346,840	327,684	304,819
Operating expenses									(159,677)	(157,014)	(129,926)
NOI - consolidated									187,163	170,670	174,893
Deduct: NOI attributable to noncontrolling interests in consolidated subsidiaries									(28,436)	(22,696)	(19,412)
Add: Our share of NOI from partially owned entities									28,222	57,656	79,837
NOI at share									186,949	205,630	235,318
Non-cash adjustments for straight-line rents, amortization of acquired below-market leases, net and other									6,258	723	(7,640)
NOI at share - cash basis									193,207	206,353	$ 227,678
Balance Sheet Data:
Real estate, at cost	2,801,554				3,885,940				2,801,554	3,885,940
Investments in partially owned entities	34,876				138,657				34,876	138,657
Assets	$ 1,857,854				$ 2,552,082				$ 1,857,854	$ 2,552,082