Investment in Unconsolidated Joint Ventures (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assets
Commercial real estate property, net	$ 12,163,976	$ 10,687,540
Other assets	647,333	750,123
Liabilities and members' equity
Mortgages and other loans payable	5,586,709	4,860,578
Company's investments in unconsolidated joint ventures	1,172,020	1,113,218
Combined statements of income for the unconsolidated joint ventures
Operating expenses	282,283	276,589	275,872
Ground rent	32,307	31,951	31,504
Real estate taxes	217,843	203,076	194,371
Interest expense, net of interest income	317,400	310,894	309,681
Amortization of deferred financing costs	22,377	15,855	18,558
Transaction related costs, net of recoveries	8,707	3,985	5,402
Depreciation and amortization	400,001	357,599	351,539
Total expenses	1,345,015	1,253,003	1,230,652
Company's equity in net income from unconsolidated joint ventures	26,537	9,921	76,418
Joint venture
Assets
Commercial real estate property, net	5,275,632	6,846,021
Other assets	810,567	827,282
Total assets	6,086,199	7,673,303
Liabilities and members' equity
Mortgages and other loans payable	3,778,704	5,066,710
Other liabilities	485,572	596,960
Members' equity	1,821,923	2,009,633
Total liabilities and members' equity	6,086,199	7,673,303
Company's investments in unconsolidated joint ventures	1,172,020	1,113,218
Combined statements of income for the unconsolidated joint ventures
Total revenues	522,132	628,649	511,157
Operating expenses	82,436	114,633	80,722
Ground rent	9,898	2,863	2,975
Real estate taxes	64,217	71,755	53,613
Interest expense, net of interest income	178,743	225,765	221,476
Amortization of deferred financing costs	12,395	17,092	9,739
Transaction related costs, net of recoveries	535	808	2,044
Depreciation and amortization	137,793	192,504	166,336
Total expenses	486,017	625,420	536,905
(Loss) gain on early extinguishment of debt	(6,743)	0	21,421
Net income (loss) before gain on sale	29,372	3,229	(4,327)
Company's equity in net income from unconsolidated joint ventures	$ 26,537	$ 9,921	$ 76,418