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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Assets
Commercial real estate property, net	$ 9,421,501		$ 9,421,501		$ 10,478,638
Cash and cash equivalents	241,489	$ 405,896	241,489	$ 405,896	279,443	$ 255,399
Tenant and other receivables, related party receivables, and deferred rents receivable, net of allowance	54,663		54,663		53,772
Other assets	395,612		395,612		614,067
Liabilities and members' equity
Mortgages and other loans payable, net	3,804,174		3,804,174		4,073,830
Deferred revenue/gain	252,779		252,779		217,955
Other liabilities	95,718		95,718		206,238
Company's investments in unconsolidated joint ventures	2,045,796		2,045,796		1,890,186
Combined statements of income for the unconsolidated joint ventures
Operating expenses	75,927	79,425	221,285	234,269
Ground rent	8,307	8,338	24,923	24,953
Real estate taxes	64,160	64,133	186,173	187,931
Interest expense, net of interest income	65,634	72,565	196,112	256,326
Amortization of deferred financing costs	4,008	4,815	12,201	20,180
Transaction related costs	186	2,593	365	5,987
Depreciation and amortization	91,728	112,665	318,916	717,015
Total expenses	333,913	369,992	1,032,337	1,520,635
Company's equity in net income (loss) from unconsolidated joint ventures	4,078	(3,968)	14,104	11,969
Joint venture
Investment in Unconsolidated Joint Ventures
Management fees, base revenue	2,900	2,000	28,100	4,500
Assets
Commercial real estate property, net	9,944,280		9,944,280		9,131,717
Cash and cash equivalents	370,596		370,596		328,455
Tenant and other receivables, related party receivables, and deferred rents receivable, net of allowance	267,244		267,244		232,778
Debt and preferred equity investments, net	201,731		201,731		336,164
Other assets	636,365		636,365		683,481
Total assets	11,420,216		11,420,216		10,712,595
Liabilities and members' equity
Mortgages and other loans payable, net	7,198,609		7,198,609		6,453,966
Deferred revenue/gain	340,310		340,310		356,414
Other liabilities	411,261		411,261		391,500
Members' equity	3,470,036		3,470,036		3,510,715
Total liabilities and members' equity	11,420,216		11,420,216		$ 10,712,595
Combined statements of income for the unconsolidated joint ventures
Total revenues	216,100	184,221	643,210	498,308
Operating expenses	38,055	34,727	115,996	89,147
Ground rent	4,182	3,744	12,612	10,670
Real estate taxes	37,282	30,814	107,391	79,356
Interest expense, net of interest income	61,066	51,789	176,096	147,876
Amortization of deferred financing costs	4,030	7,155	17,994	17,667
Transaction related costs	0	5,359	146	5,359
Depreciation and amortization	61,447	56,890	198,556	132,035
Total expenses	206,062	190,478	628,791	482,110
Loss on early extinguishment of debt	(7,638)	0	(7,638)	(1,606)
Net income (loss) before gain on sale	2,400	(6,257)	6,781	14,592
Company's equity in net income (loss) from unconsolidated joint ventures	$ 4,078	$ (3,968)	$ 14,104	$ 11,969