Quarterly Financial Data (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended			3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013
Unaudited Quarterly Financial Data [Line Items]
Operating income	$ 921,375	$ 512,322	$ 514,093
Income (loss) from continuing operations	657,101	(168,174)	160,298
Discontinued operations, net	1,582	2,073,527	720,906
Net income	658,683	1,905,353	881,204
Earnings Per Share, Basic [Abstract]
Net income available to Common Shares	$ 1.736	$ 5.155	$ 2.729
Weighted average Common Shares outstanding	361,181	354,305	302,701
Earnings Per Share, Diluted [Abstract]
Net income available to Common Shares	$ 1.726	$ 5.155	$ 2.705
Weighted Average Number of Shares Outstanding, Diluted	377,735	354,305	319,766
Scenario, Previously Reported [Member]
Unaudited Quarterly Financial Data [Line Items]
Total revenues				664,660	664,078	652,568	633,442	639,134	626,629	617,217	504,722
Operating income				250,532	243,274	228,310	199,259	223,677	120,405	63,986	104,254
Income (loss) from continuing operations				226,959	231,252	117,210	81,680	69,141	(13,465)	(58,511)	(165,339)
Discontinued operations, net				82	(62)	510	1,052	46,729	405,182	395,243	1,226,373
Net income				227,041	231,190	117,720	82,732	115,870	391,717	336,732	1,061,034
Net income available to Common Shares				216,703	220,707	111,654	78,099	109,940	376,155	323,723	1,016,650
Earnings Per Share, Basic [Abstract]
Net income available to Common Shares				$ 0.60	$ 0.61	$ 0.31	$ 0.22	$ 0.31	$ 1.05	$ 0.90	$ 3.01
Weighted average Common Shares outstanding				362,018	361,409	360,809	360,470	359,919	359,811	359,653	337,532
Earnings Per Share, Diluted [Abstract]
Net income available to Common Shares				$ 0.59	$ 0.61	$ 0.31	$ 0.22	$ 0.30	$ 1.05	$ 0.90	$ 3.01
Weighted Average Number of Shares Outstanding, Diluted				378,886	377,954	377,118	376,384	375,860	359,811	359,653	337,532
Operating Partnership [Member] | Scenario, Previously Reported [Member]
Unaudited Quarterly Financial Data [Line Items]
Total revenues				664,660	664,078	652,568	633,442	639,134	626,629	617,217	504,722
Operating income				250,532	243,274	228,310	199,259	223,677	120,405	63,986	104,254
Income (loss) from continuing operations				226,959	231,252	117,210	81,680	69,141	(13,465)	(58,511)	(165,339)
Discontinued operations, net				82	(62)	510	1,052	46,729	405,182	395,243	1,226,373
Net income				227,041	231,190	117,720	82,732	115,870	391,717	336,732	1,061,034
Net income available to Units				$ 225,261	$ 229,445	$ 116,096	$ 81,192	$ 114,271	$ 390,991	$ 336,511	$ 1,059,973
Earnings Per Share, Basic [Abstract]
Net income available to Common Shares				$ 0.60	$ 0.61	$ 0.31	$ 0.22	$ 0.31	$ 1.05	$ 0.90	$ 3.01
Weighted average Units outstanding				375,711	375,116	374,551	374,201	373,643	373,547	373,403	351,255
Earnings Per Share, Diluted [Abstract]
Net income available to Common Shares				$ 0.59	$ 0.61	$ 0.31	$ 0.22	$ 0.30	$ 1.05	$ 0.90	$ 3.01
Weighted average Units outstanding				378,886	377,954	377,118	376,384	375,860	373,547	373,403	351,255