Quarterly Financial Data (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Unaudited Quarterly Financial Data [Line Items]
Total revenues		$ 626,629	$ 617,217	$ 504,722	$ 452,483	$ 449,072	$ 431,910	$ 414,037
Total revenues subsequently reclassified to discontinued operations		(2,817)	(17,861)	(34,440)	(33,385)	(2,627)	(16,441)	(32,411)
Operating income		120,396	63,977	104,246	148,247	142,020	121,745	102,110	512,288	514,122	406,509
Operating income subsequently reclassified to discontinued operations		(998)	(7,056)	(13,283)	(13,862)	(912)	(6,815)	(12,366)
(Loss) income from continuing operations		(13,465)	(58,511)	(165,339)	100,763	91,269	(6,340)	(25,394)	(168,174)	160,298	(72,941)
Income from continuing operations subsequently reclassified to discontinued operations		(998)	(7,056)	(11,987)	(13,476)	(912)	(6,814)	(11,968)
Discontinued operations, net		405,182	395,243	1,226,373	283,636	145,054	114,655	177,561	2,073,527	720,906	1,008,138
Discontinued operations, net from properties sold subsequent to the respective reporting period		998	7,056	11,987	13,476	912	6,814	11,968
Net income									1,905,353	881,204	935,197
Net income available to Common Shares	109,940	376,155	323,723	1,016,650	365,979	218,603	99,797	141,833	1,826,468	826,212	879,720
Net Income per share - basis	$ 0.31	$ 1.05	$ 0.90	$ 3.01	$ 1.18	$ 0.73	$ 0.33	$ 0.47	$ 5.155	$ 2.729	$ 2.984
Weighted Average Number of Shares Outstanding, Basic	359,919	359,811	359,653	337,532	310,398	301,336	300,193	298,805	354,305	302,701	294,856
Net income per share - diluted	$ 0.30	$ 1.05	$ 0.90	$ 3.01	$ 1.17	$ 0.72	$ 0.33	$ 0.47	$ 5.155	$ 2.705	$ 2.984
Weighted average Common Shares outstanding	375,860	359,811	359,653	337,532	327,108	318,773	300,193	298,805	354,305	319,766	294,856
Operating Partnership [Member]
Unaudited Quarterly Financial Data [Line Items]
Total revenues	639,134	626,629	617,217	504,722	452,483	449,072	431,910	414,037
Total revenues subsequently reclassified to discontinued operations		(2,817)	(17,861)	(34,440)	(33,385)	(2,627)	(16,441)	(32,411)
Operating income	223,669	120,396	63,977	104,246	148,247	142,020	121,745	102,110
Operating income subsequently reclassified to discontinued operations		(998)	(7,056)	(13,283)	(13,862)	(912)	(6,815)	(12,366)
(Loss) income from continuing operations	69,141	(13,465)	(58,511)	(165,339)	100,763	91,269	(6,340)	(25,394)
Income from continuing operations subsequently reclassified to discontinued operations		(998)	(7,056)	(11,987)	(13,476)	(912)	(6,814)	(11,968)
Discontinued operations, net	46,729	405,182	395,243	1,226,373	283,636	145,054	114,655	177,561
Discontinued operations, net from properties sold subsequent to the respective reporting period		998	7,056	11,987	13,476	912	6,814	11,968
Net income	115,870	391,717	336,732	1,061,034	384,399	236,323	108,315	152,167
Net income available to Units	114,271	390,991	336,511	1,059,973	382,974	229,099	104,529	148,251
Net Income per share - basis	$ 0.31	$ 1.05	$ 0.90	$ 3.01	$ 1.18	$ 0.73	$ 0.33	$ 0.47
Net income per share - diluted	$ 0.30	$ 1.05	$ 0.90	$ 3.01	$ 1.17	$ 0.72	$ 0.33	$ 0.47
Weighted average Units outstanding	373,643	373,547	373,403	351,255	324,364	315,513	314,255	312,011
Weighted average Units outstanding	375,860	373,547	373,403	351,255	327,108	318,773	314,255	312,011
Scenario, Previously Reported [Member]
Unaudited Quarterly Financial Data [Line Items]
Total revenues		629,446	635,078	539,162	485,868	451,699	448,351	446,448
Operating income		121,394	71,033	117,529	162,109	142,932	128,560	114,476
(Loss) income from continuing operations		(12,467)	(51,455)	(153,352)	114,239	92,181	474	(13,426)
Discontinued operations, net		404,184	388,187	1,214,386	270,160	144,142	107,841	165,593
Scenario, Previously Reported [Member] | Operating Partnership [Member]
Unaudited Quarterly Financial Data [Line Items]
Total revenues		629,446	635,078	539,162	485,868	451,699	448,351	446,448
Operating income		121,394	71,033	117,529	162,109	142,932	128,560	114,476
(Loss) income from continuing operations		(12,467)	(51,455)	(153,352)	114,239	92,181	474	(13,426)
Discontinued operations, net		$ 404,184	$ 388,187	$ 1,214,386	$ 270,160	$ 144,142	$ 107,841	$ 165,593