Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unaudited Quarterly Financial Data [Line Items]
Total revenues									$ 2,578,434	$ 2,471,406	$ 2,425,800
Operating income									858,560	847,471	856,086
Net income									685,192	628,381	4,480,104
Net income available to Common Shares									$ 654,445	$ 600,363	$ 4,289,072
Earnings per share – basic:
Net income available to Common Shares									$ 1.78	$ 1.64	$ 11.75
Weighted average Common Shares outstanding									368,052	366,968	365,002
Earnings per share – diluted:
Net income available to Common Shares									$ 1.77	$ 1.63	$ 11.68
Weighted average Common Shares outstanding									383,695	382,678	381,992
ERPOP [Member]
Unaudited Quarterly Financial Data [Line Items]
Total revenues									$ 2,578,434	$ 2,471,406	$ 2,425,800
Operating income									858,560	847,471	856,086
Net income									685,192	628,381	4,480,104
Net income available to Units									$ 679,384	$ 622,967	$ 4,460,583
Earnings per share – basic:
Net income available to Common Shares									$ 1.78	$ 1.64	$ 11.75
Weighted average Units outstanding									380,921	379,869	378,829
Earnings per share – diluted:
Net income available to Common Shares									$ 1.77	$ 1.63	$ 11.68
Weighted average Common Shares outstanding									383,695	382,678	381,992
Scenario, Previously Reported [Member]
Unaudited Quarterly Financial Data [Line Items]
Total revenues	$ 652,743	$ 652,867	$ 639,808	$ 633,016	$ 630,704	$ 624,122	$ 612,480	$ 604,100
Operating income	219,306	224,731	217,654	196,869	214,764	217,786	210,550	204,371
Net income	122,388	223,846	118,410	220,548	130,084	144,196	204,160	149,941
Net income available to Common Shares	$ 116,415	$ 214,164	$ 112,830	$ 211,036	$ 124,669	$ 137,457	$ 195,268	$ 142,969
Earnings per share – basic:
Net income available to Common Shares	$ 0.32	$ 0.58	$ 0.31	$ 0.57	$ 0.34	$ 0.37	$ 0.53	$ 0.39
Weighted average Common Shares outstanding	368,445	368,028	367,930	367,800	367,442	366,996	366,820	366,605
Earnings per share – diluted:
Net income available to Common Shares	$ 0.31	$ 0.58	$ 0.31	$ 0.57	$ 0.34	$ 0.37	$ 0.53	$ 0.39
Weighted average Common Shares outstanding	384,296	383,884	383,423	383,018	383,105	382,945	382,692	382,280
Scenario, Previously Reported [Member] | ERPOP [Member]
Unaudited Quarterly Financial Data [Line Items]
Total revenues	$ 652,743	$ 652,867	$ 639,808	$ 633,016	$ 630,704	$ 624,122	$ 612,480	$ 604,100
Operating income	219,306	224,731	217,654	196,869	214,764	217,786	210,550	204,371
Net income	122,388	223,846	118,410	220,548	130,084	144,196	204,160	149,941
Net income available to Units	$ 120,837	$ 222,323	$ 117,129	$ 219,095	$ 129,342	$ 142,623	$ 202,622	$ 148,380
Earnings per share – basic:
Net income available to Common Shares	$ 0.32	$ 0.58	$ 0.31	$ 0.57	$ 0.34	$ 0.37	$ 0.53	$ 0.39
Weighted average Units outstanding	381,306	380,912	380,795	380,663	380,325	379,906	379,733	379,504
Earnings per share – diluted:
Net income available to Common Shares	$ 0.31	$ 0.58	$ 0.31	$ 0.57	$ 0.34	$ 0.37	$ 0.53	$ 0.39
Weighted average Units outstanding	384,296	383,884	383,423	383,018	383,105	382,945	382,692	382,280