Investments in Unconsolidated Joint Ventures - Schedules of Combined Financial Statements for the Unconsolidated Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Assets
Commercial real estate property, net	$ 6,524,929		$ 6,524,929		$ 7,906,006
Cash and cash equivalents	160,248	$ 241,489	160,248	$ 241,489	127,888
Tenant and other receivables, related party receivables, and deferred rents receivable, net of allowance	44,614		44,614		57,644
Other assets	301,130		301,130		310,688
Liabilities and equity
Mortgages and other loans payable, net	2,316,688		2,316,688		2,837,282
Deferred revenue/gain	110,283		110,283		208,119
Other liabilities	97,565		97,565		188,005
Company's investments in unconsolidated joint ventures	3,070,825		3,070,825		2,362,989
Combined statements of income for the unconsolidated joint ventures
Operating expenses	56,852	75,927	172,871	221,285
Ground rent	9,507	8,307	26,661	24,923
Real estate taxes	48,805	64,160	139,788	186,173
Interest expense, net of interest income	55,168	65,634	156,695	196,112
Amortization of deferred financing costs	2,630	4,008	9,713	12,201
Transaction related costs	163	186	673	365
Depreciation and amortization	70,747	91,728	208,049	318,916
Total expenses	265,553	333,913	782,138	1,032,337
Loss on early extinguishment of debt	(2,194)	0	(2,194)	0
Company's equity in net income from unconsolidated joint ventures (1)	971	4,078	9,709	14,104
Joint venture
Investment in Unconsolidated Joint Ventures
Management fees, base revenue	2,400	1,500	9,300	19,400
Assets
Commercial real estate property, net	14,091,365		14,091,365		12,822,133
Cash and cash equivalents	350,802		350,802		494,909
Tenant and other receivables, related party receivables, and deferred rents receivable, net of allowance	287,509		287,509		349,944
Debt and preferred equity investments, net	189,427		189,427		202,539
Other assets	2,235,237		2,235,237		1,407,806
Total assets	17,154,340		17,154,340		15,277,331
Liabilities and equity
Mortgages and other loans payable, net	9,164,061		9,164,061		9,412,101
Deferred revenue/gain	1,851,079		1,851,079		985,648
Other liabilities	474,169		474,169		411,053
Equity	5,665,031		5,665,031		4,468,529
Total liabilities and equity	17,154,340		17,154,340		15,277,331
Company's investments in unconsolidated joint ventures	3,070,825		3,070,825		$ 2,362,989
Combined statements of income for the unconsolidated joint ventures
Total revenues	304,869	216,100	940,005	643,210
Operating expenses	56,304	38,055	166,433	115,996
Ground rent	4,397	4,182	13,247	12,612
Real estate taxes	56,747	37,282	169,612	107,391
Interest expense, net of interest income	88,328	61,066	269,717	176,096
Amortization of deferred financing costs	4,446	4,030	16,912	17,994
Transaction related costs	0	0	0	146
Depreciation and amortization	101,538	61,447	318,113	198,556
Total expenses	311,760	206,062	954,034	628,791
Loss on early extinguishment of debt	0	(7,638)	0	(7,638)
Net (loss) income before gain on sale (1)	(6,891)	2,400	(14,029)	6,781
Company's equity in net income from unconsolidated joint ventures (1)	$ 971	$ 4,078	$ 9,709	$ 14,104