Investments in Unconsolidated Joint Ventures - Schedules of Combined Financial Statements for the Unconsolidated Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Assets (1)
Commercial real estate property, net	$ 6,595,221		$ 6,595,221		$ 7,906,006
Cash and cash equivalents	287,240	$ 270,965	287,240	$ 270,965	127,888
Tenant and other receivables, related party receivables, and deferred rents receivable, net of allowance	47,482		47,482		57,644
Other assets	290,729		290,729		310,688
Liabilities and equity (1)
Mortgages and other loans payable, net	2,517,097		2,517,097		2,837,282
Deferred revenue/gain	95,756		95,756		208,119
Other liabilities	108,151		108,151		188,005
Company's investments in unconsolidated joint ventures	3,059,985		3,059,985		2,362,989
Combined statements of income for the unconsolidated joint ventures
Operating expenses	56,237	70,852	116,019	145,358
Ground rent	8,846	8,308	17,154	16,616
Real estate taxes	45,322	60,945	90,983	122,013
Interest expense, net of interest income	53,611	64,856	101,527	130,478
Amortization of deferred financing costs	3,546	3,432	7,083	8,193
Transaction related costs	348	46	510	179
Depreciation and amortization	67,914	133,054	137,302	227,188
Total expenses	258,303	365,749	516,585	698,424
Company's equity in net income from unconsolidated joint ventures (1)	4,702	3,412	8,738	10,026
Joint venture
Investment in Unconsolidated Joint Ventures
Management fees, base revenue	3,000	12,400	6,900	17,900
Assets (1)
Commercial real estate property, net	14,193,325		14,193,325		12,822,133
Cash and cash equivalents	434,307		434,307		494,909
Tenant and other receivables, related party receivables, and deferred rents receivable, net of allowance	308,653		308,653		349,944
Debt and preferred equity investments, net	228,588		228,588		202,539
Other assets	2,254,990		2,254,990		1,407,806
Total assets	17,419,863		17,419,863		15,277,331
Liabilities and equity (1)
Mortgages and other loans payable, net	9,433,738		9,433,738		9,412,101
Deferred revenue/gain	1,863,384		1,863,384		985,648
Other liabilities	478,916		478,916		411,053
Equity	5,643,825		5,643,825		4,468,529
Total liabilities and equity	17,419,863		17,419,863		15,277,331
Company's investments in unconsolidated joint ventures	3,059,985		3,059,985		$ 2,362,989
Combined statements of income for the unconsolidated joint ventures
Total revenues	314,195	210,590	635,136	427,109
Operating expenses	50,356	39,147	110,129	77,941
Ground rent	4,457	4,179	8,850	8,430
Real estate taxes	55,838	35,170	112,865	70,109
Interest expense, net of interest income	91,648	59,702	181,389	115,030
Amortization of deferred financing costs	7,350	7,458	12,466	13,963
Transaction related costs	0	56	0	146
Depreciation and amortization	111,495	65,944	216,575	137,109
Total expenses	321,144	211,656	642,274	422,728
Net (loss) income before gain on sale (1)	(6,949)	(1,066)	(7,138)	4,381
Company's equity in net income from unconsolidated joint ventures (1)	$ 4,702	$ 3,412	$ 8,738	$ 10,026