Investments in Unconsolidated Joint Ventures (Details 3) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Assets
Commercial real estate property, net	$ 14,261,102		$ 14,261,102		$ 12,163,976
Other assets	912,023		912,023		647,333
Liabilities and members' equity
Mortgages and other loans payable	6,865,383		6,865,383		5,586,709
Company's investments in unconsolidated joint ventures	1,239,008		1,239,008		1,172,020
Combined statements of income for the unconsolidated joint ventures
Operating expenses	78,648	$ 72,111	225,539	$ 211,118
Ground rent	8,252	8,088	24,526	24,161
Real estate taxes	61,009	55,548	173,018	159,702
Interest expense, net of interest income	84,141	82,376	235,694	236,424
Amortization of deferred financing costs	7,160	6,679	19,727	15,737
Transaction related costs	5,829	2,383	10,039	6,554
Depreciation and amortization	146,185	94,443	454,087	274,337
Total expenses	414,699	344,277	1,214,769	997,811
Company's equity in net income from unconsolidated joint ventures	3,627	6,034	10,651	20,781
Joint venture
Assets
Commercial real estate property, net	6,282,267		6,282,267		5,275,632
Other assets	906,955		906,955		810,567
Total assets	7,189,222		7,189,222		6,086,199
Liabilities and members' equity
Mortgages and other loans payable	4,413,802		4,413,802		3,778,704
Other liabilities	501,637		501,637		485,572
Members' equity	2,273,783		2,273,783		1,821,923
Total liabilities and members' equity	7,189,222		7,189,222		6,086,199
Company's investments in unconsolidated joint ventures	1,239,008		1,239,008		$ 1,172,020
Combined statements of income for the unconsolidated joint ventures
Total revenues	150,638	114,831	423,089	406,464
Operating expenses	27,647	18,530	79,478	63,575
Ground rent	4,677	2,638	9,841	7,295
Real estate taxes	23,494	15,867	65,205	48,209
Interest expense, net of interest income	51,430	40,885	147,152	137,949
Amortization of deferred financing costs	3,473	2,837	9,628	9,496
Transaction related costs	604	501	615	565
Depreciation and amortization	38,144	28,324	109,022	107,786
Total expenses	149,469	109,582	420,941	374,875
Loss on early extinguishment of debt	(248)	0	(1,081)	(6,743)
Net income before gain on sale	921	5,249	1,067	24,846
Company's equity in net income from unconsolidated joint ventures	3,627	6,034	10,651	20,781
Joint venture
Investment in Unconsolidated Joint Ventures
Management fees, base revenue	$ 1,900	$ 3,800	$ 6,800	$ 15,000