Segment Disclosures - NOI (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of reported net income to NOI and adjusted NOI
Net income	$ 199,630	$ 251,059	$ 222,279	$ 263,623	$ 297,639	$ 236,858	$ 216,725	$ 233,784	$ 936,591	$ 985,006	$ 846,842
Interest income									(74,491)	(86,159)	(24,536)
Investment management fee income									(1,809)	(1,847)	(1,895)
Interest expense									439,742	435,252	416,172
Depreciation and amortization									459,995	423,312	353,704
General and administrative									82,175	103,042	68,414
Business Combination, Acquisition Related Costs									17,142	6,191	10,981
Impairments											7,878
Gain on sales of real estate, net of income taxes									(3,288)
Other non-operating income, net									(7,528)	(18,216)	(2,976)
Income taxes									250	5,815	(1,654)
Equity income from unconsolidated joint ventures									(49,570)	(64,433)	(54,455)
Equity Method Investment, Other than Temporary Impairment									35,913
Total discontinued operations				(29,746)	(59,489)	(9,824)	(2,828)	(2,232)	(29,746)	(74,373)	(45,652)
NOI									1,805,376	1,713,590	1,572,823
Straight-line rents									(41,032)	(39,587)	(47,311)
DFL accretion									(77,568)	(86,055)	(94,240)
Amortization of above and below market lease intangibles, net									(949)	(6,646)	(2,232)
Lease termination fees									(38,816)	(217)	(636)
NOI adjustments related to discontinued operations									(11)	(47)	1,585
Adjusted (Cash) NOI									$ 1,647,000	$ 1,581,038	$ 1,429,989