Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Unaudited Quarterly Financial Data [Line Items]
Revenues									$ 2,744,965	$ 2,614,748	$ 2,387,702
Operating income									1,008,820	921,375	512,322
Income (loss) from continuing operations									907,621	657,101	(168,174)
Discontinued operations, net									397	1,582	2,073,527
Net income									908,018	658,683	1,905,353
Net income available to Common Shares									$ 863,277	$ 627,163	$ 1,826,468
Earnings Per Share, Basic [Abstract]
Net income available to Common Shares									$ 2.37	$ 1.74	$ 5.16
Weighted average Common Shares outstanding									363,498	361,181	354,305
Earnings Per Share, Diluted [Abstract]
Net income available to Common Shares									$ 2.36	$ 1.73	$ 5.16
Weighted average Common Shares outstanding									380,620	377,735	354,305
Scenario, Previously Reported [Member]
Unaudited Quarterly Financial Data [Line Items]
Revenues	$ 703,193	$ 696,289	$ 679,112	$ 666,371	$ 664,660	$ 664,078	$ 652,568	$ 633,442
Operating income	286,964	257,501	246,184	218,171	250,532	243,274	228,310	199,259
Income (loss) from continuing operations	213,673	205,375	298,504	190,069	226,959	231,252	117,210	81,680
Discontinued operations, net	47	81	114	155	82	(62)	510	1,052
Net income	213,720	205,456	298,618	190,224	227,041	231,190	117,720	82,732
Net income available to Common Shares	$ 202,989	$ 195,859	$ 285,587	$ 178,842	$ 216,703	$ 220,707	$ 111,654	$ 78,099
Earnings Per Share, Basic [Abstract]
Net income available to Common Shares	$ 0.56	$ 0.54	$ 0.79	$ 0.49	$ 0.60	$ 0.61	$ 0.31	$ 0.22
Weighted average Common Shares outstanding	363,828	363,579	363,476	363,098	362,018	361,409	360,809	360,470
Earnings Per Share, Diluted [Abstract]
Net income available to Common Shares	$ 0.55	$ 0.53	$ 0.78	$ 0.49	$ 0.59	$ 0.61	$ 0.31	$ 0.22
Weighted average Common Shares outstanding	381,220	380,663	380,491	380,327	378,886	377,954	377,118	376,384
ERPOP [Member]
Unaudited Quarterly Financial Data [Line Items]
Revenues									$ 2,744,965	$ 2,614,748	$ 2,387,702
Operating income									1,008,820	921,375	512,322
Income (loss) from continuing operations									907,621	657,101	(168,174)
Discontinued operations, net									397	1,582	2,073,527
Net income									908,018	658,683	1,905,353
Net income available to Units									$ 897,518	$ 651,994	$ 1,901,746
Earnings Per Share, Basic [Abstract]
Net income available to Common Shares									$ 2.37	$ 1.74	$ 5.16
Weighted average Units outstanding									377,074	374,899	368,038
Earnings Per Share, Diluted [Abstract]
Net income available to Common Shares									$ 2.36	$ 1.73	$ 5.16
Weighted average Common Shares outstanding									380,620	377,735	368,038
ERPOP [Member] | Scenario, Previously Reported [Member]
Unaudited Quarterly Financial Data [Line Items]
Revenues	$ 703,193	$ 696,289	$ 679,112	$ 666,371	$ 664,660	$ 664,078	$ 652,568	$ 633,442
Operating income	286,964	257,501	246,184	218,171	250,532	243,274	228,310	199,259
Income (loss) from continuing operations	213,673	205,375	298,504	190,069	226,959	231,252	117,210	81,680
Discontinued operations, net	47	81	114	155	82	(62)	510	1,052
Net income	213,720	205,456	298,618	190,224	227,041	231,190	117,720	82,732
Net income available to Units	$ 211,039	$ 203,637	$ 296,941	$ 185,901	$ 225,261	$ 229,445	$ 116,096	$ 81,192
Earnings Per Share, Basic [Abstract]
Net income available to Common Shares	$ 0.56	$ 0.54	$ 0.79	$ 0.49	$ 0.60	$ 0.61	$ 0.31	$ 0.22
Weighted average Units outstanding	377,380	377,147	377,063	376,696	375,711	375,116	374,551	374,201
Earnings Per Share, Diluted [Abstract]
Net income available to Common Shares	$ 0.55	$ 0.53	$ 0.78	$ 0.49	$ 0.59	$ 0.61	$ 0.31	$ 0.22
Weighted average Units outstanding	381,220	380,663	380,491	380,327	378,886	377,954	377,118	376,384