Investments in Unconsolidated Joint Ventures (Schedules of Combined Financial Statements for the Unconsolidated Joint Ventures)(Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets
Commercial real estate property, net	$ 10,478,638				$ 14,620,896				$ 10,478,638	$ 14,620,896
Cash and cash equivalents	279,443				255,399				279,443	255,399	$ 281,409	$ 206,692
Tenant and other receivables, related party receivables, and deferred rents receivable, net of allowance	53,772				63,491				53,772	63,491
Other assets	614,067				850,939				614,067	850,939
Liabilities and members' equity
Mortgages and other loans payable, net	4,073,830				6,881,920				4,073,830	6,881,920
Deferred revenue	217,955				399,102				217,955	399,102
Other liabilities	206,238				168,477				206,238	168,477
Company's investments in unconsolidated joint ventures	1,890,186				1,203,858				1,890,186	1,203,858
Combined statements of income for the unconsolidated joint ventures
Operating expenses									312,859	301,624	282,283
Ground rent									33,261	32,834	32,307
Real estate taxes									248,388	232,702	217,843
Interest expense, net of interest income									321,199	323,870	317,400
Amortization of deferred financing costs									24,564	27,348	22,377
Transaction related costs									7,528	11,430	8,707
Depreciation and amortization									821,041	560,887	371,610
Total expenses									1,868,599	1,585,568	1,345,015
Company's equity in net income from unconsolidated joint ventures	(95)	$ (3,968)	$ 5,841	$ 10,096	2,377	$ 3,627	$ 2,994	$ 4,030	11,874	13,028	26,537
Joint venture
Investment in Unconsolidated Joint Ventures
Management fees, base revenue									8,100	6,900	16,900
Assets
Commercial real estate property, net	9,131,717				6,122,468				9,131,717	6,122,468
Cash and cash equivalents	328,455				258,564				328,455	258,564
Tenant and other receivables, related party receivables, and deferred rents receivable, net of allowance	232,778				208,802				232,778	208,802
Debt and preferred equity investments, net	336,164				145,878				336,164	145,878
Other assets	683,481				248,474				683,481	248,474
Total assets	10,712,595				6,984,186				10,712,595	6,984,186
Liabilities and members' equity
Mortgages and other loans payable, net	6,453,966				4,266,548				6,453,966	4,266,548
Deferred revenue	356,414				209,095				356,414	209,095
Other liabilities	391,500				314,065				391,500	314,065
Members' equity	3,510,715				2,194,478				3,510,715	2,194,478
Total liabilities and members' equity	$ 10,712,595				$ 6,984,186				10,712,595	6,984,186
Combined statements of income for the unconsolidated joint ventures
Total revenues									712,689	576,845	522,132
Operating expenses									126,913	106,613	82,436
Ground rent									14,924	14,083	9,898
Real estate taxes									111,673	89,734	64,217
Interest expense, net of interest income									197,741	199,126	178,743
Amortization of deferred financing costs									24,829	13,394	12,395
Transaction related costs									5,566	615	535
Depreciation and amortization									199,011	149,023	137,793
Total expenses									680,657	572,588	486,017
Loss on early extinguishment of debt									(1,606)	(1,089)	(6,743)
Net income before gain on sale									30,426	3,168	29,372
Company's equity in net income from unconsolidated joint ventures									$ 11,874	$ 13,028	$ 26,537