Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income from continuing operations	$ 217,246	$ 205,375	$ 4,177,599	$ 693,948
Allocation to Noncontrolling Interests – Operating Partnership, net	(8,344)	(7,775)	(160,437)	(26,178)
Net (income) attributable to Noncontrolling Interests – Partially Owned Properties	(823)	(986)	(2,368)	(2,473)
Preferred distributions	(773)	(833)	(2,318)	(2,557)
Premium on redemption of Preferred Shares	0	0	0	(2,789)
Income from continuing operations available to Common Shares, net of Noncontrolling Interests	207,306	195,781	4,012,476	659,951
Discontinued operations, net of Noncontrolling Interests	237	78	119	337
Numerator for net income per share – basic	207,543	195,859	4,012,595	660,288
Income from continuing operations available to Common Shares	215,650	203,556	4,172,913	686,129
Discontinued operations, net	246	81	124	350
Numerator for net income per share – diluted	$ 215,896	$ 203,637	$ 4,173,037	$ 686,479
Denominator for net income per share – basic	365,109	363,579	364,917	363,386
Effect of dilutive securities - OP Units	13,899	13,568	13,828	13,584
Effect of dilutive securities - Long-term compensation shares/units	3,365	3,516	3,539	3,453
Denominator for net income per share – diluted	382,373	380,663	382,284	380,423
Net income available to Common Shares	$ 0.57	$ 0.54	$ 11.00	$ 1.82
Net income available to Common Shares	0.56	0.53	10.92	1.80
Income from continuing operations available to Common Shares	0.57	0.54	11.00	1.82
Net income per share - basic - Discontinued operations, net of Noncontrolling Interests	0.00	0.00	0.00	0.00
Income from continuing operations available to Common Shares	0.56	0.53	10.92	1.80
Net income per share - diluted - discontinued operations, net	$ 0.00	$ 0.00	$ 0.00	$ 0.00
ERPOP [Member]
Income from continuing operations	$ 217,246	$ 205,375	$ 4,177,599	$ 693,948
Net (income) attributable to Noncontrolling Interests – Partially Owned Properties	(823)	(986)	(2,368)	(2,473)
Allocation to Preference Units	(773)	(833)	(2,318)	(2,557)
Premium on redemption of Preferred Shares	0	0	0	(2,789)
Discontinued operations, net	$ 246	$ 81	$ 124	$ 350
Effect of dilutive securities - Long-term compensation shares/units	3,365	3,516	3,539	3,453
Denominator for net income per share – diluted	382,373	380,663	382,284	380,423
Net income available to Common Shares	$ 0.57	$ 0.54	$ 11.00	$ 1.82
Net income available to Common Shares	0.56	0.53	10.92	1.80
Income from continuing operations available to Common Shares	0.57	0.54	11.00	1.82
Income from continuing operations available to Common Shares	$ 0.56	$ 0.53	$ 10.92	$ 1.80
Income from continuing operations available to Units	$ 215,650	$ 203,556	$ 4,172,913	$ 686,129
Numerator for net income per Unit – basic and diluted	$ 215,896	$ 203,637	$ 4,173,037	$ 686,479
Denominator for net income per Unit – basic	379,008	377,147	378,745	376,970
Net income per Unit - basic - Discontinued operations, net	$ 0.00	$ 0.00	$ 0.00	$ 0.00
Net income per Unit - diluted - Discontinued operations, net	$ 0.00	$ 0.00	$ 0.00	$ 0.00