Investments in Unconsolidated Joint Ventures - Schedules of Combined Financial Statements for the Unconsolidated Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Assets (1)
Commercial real estate property, net	$ 6,828,550		$ 7,906,006
Cash and cash equivalents	288,808	$ 468,035	127,888
Tenant and other receivables, related party receivables, and deferred rents receivable, net of allowance	49,552		57,644
Other assets	360,556		310,688
Liabilities and equity (1)
Mortgages and other loans payable, net	2,433,994		2,837,282
Deferred revenue/gain	177,896		208,119
Other liabilities	103,654		188,005
Company's investments in unconsolidated joint ventures	3,034,596		2,362,989
Combined statements of income for the unconsolidated joint ventures
Operating expenses	59,782	74,506
Ground rent	8,308	8,308
Real estate taxes	45,661	61,068
Interest expense, net of interest income	47,916	65,622
Amortization of deferred financing costs	3,537	4,761
Transaction related costs	162	133
Depreciation and amortization	69,388	94,134
Total expenses	258,282	332,675
Company's equity in net income from unconsolidated joint ventures (1)	4,036	6,614
Joint venture
Investment in Unconsolidated Joint Ventures
Management fees, base revenue	3,800	5,400
Assets (1)
Commercial real estate property, net	14,652,483		12,822,133
Cash and cash equivalents	452,648		494,909
Tenant and other receivables, related party receivables, and deferred rents receivable, net of allowance	359,396		349,944
Debt and preferred equity investments, net	103,379		202,539
Other assets	2,361,367		1,407,806
Total assets	17,929,273		15,277,331
Liabilities and equity (1)
Mortgages and other loans payable, net	9,876,879		9,412,101
Deferred revenue/gain	1,911,564		985,648
Other liabilities	493,369		411,053
Members' equity	5,647,461		4,468,529
Total liabilities and members' equity	17,929,273		15,277,331
Company's investments in unconsolidated joint ventures	3,034,596		$ 2,362,989
Combined statements of income for the unconsolidated joint ventures
Total revenues	320,941	216,521
Operating expenses	59,773	38,794
Ground rent	4,393	4,251
Real estate taxes	57,027	34,939
Interest expense, net of interest income	89,741	55,328
Amortization of deferred financing costs	5,116	6,505
Transaction related costs	0	89
Depreciation and amortization	105,080	71,164
Total expenses	321,130	211,070
Net (loss) income before gain on sale (1)	(189)	5,451
Company's equity in net income from unconsolidated joint ventures (1)	$ 4,036	$ 6,614