Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income from continuing operations	$ 228,365	$ 298,504	$ 3,960,353	$ 488,573
Allocation to Noncontrolling Interests – Operating Partnership, net	(8,779)	(11,350)	(152,093)	(18,403)
Net (income) attributable to Noncontrolling Interests – Partially Owned Properties	(781)	(844)	(1,545)	(1,487)
Preferred distributions	(772)	(833)	(1,545)	(1,724)
Premium on redemption of Preferred Shares	0	0	0	(2,789)
Income from continuing operations available to Common Shares, net of Noncontrolling Interests	218,033	285,477	3,805,170	464,170
Discontinued operations, net of Noncontrolling Interests	34	110	(118)	259
Numerator for net income per share – basic	218,067	285,587	3,805,052	464,429
Income from continuing operations available to Common Shares	226,812	296,827	3,957,263	482,573
Discontinued operations, net	35	114	(122)	269
Numerator for net income per share – diluted	$ 226,847	$ 296,941	$ 3,957,141	$ 482,842
Denominator for net income per share – basic	365,047	363,476	364,820	363,288
Effect of dilutive securities - OP Units	13,887	13,587	13,792	13,592
Effect of dilutive securities - Long-term compensation shares/units	3,131	3,428	3,400	3,466
Denominator for net income per share – diluted	382,065	380,491	382,012	380,346
Net income available to Common Shares	$ 0.60	$ 0.79	$ 10.43	$ 1.28
Net income available to Common Shares	0.59	0.78	10.36	1.27
Income from continuing operations available to Common Shares	0.60	0.79	10.43	1.28
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	0.59	0.78	10.36	1.27
Net income per share - diluted - discontinued operations, net	$ 0.00	$ 0.00	$ 0.00	$ 0.00
ERPOP [Member]
Income from continuing operations	$ 228,365	$ 298,504	$ 3,960,353	$ 488,573
Net (income) attributable to Noncontrolling Interests – Partially Owned Properties	(781)	(844)	(1,545)	(1,487)
Allocation to Preference Units	(772)	(833)	(1,545)	(1,724)
Premium on redemption of Preferred Shares	0	0	0	(2,789)
Discontinued operations, net	$ 35	$ 114	$ (122)	$ 269
Effect of dilutive securities - Long-term compensation shares/units	3,131	3,428	3,400	3,466
Denominator for net income per share – diluted	382,065	380,491	382,012	380,346
Net income available to Common Shares	$ 0.60	$ 0.79	$ 10.43	$ 1.28
Net income available to Common Shares	0.59	0.78	10.36	1.27
Income from continuing operations available to Common Shares	0.60	0.79	10.43	1.28
Income from continuing operations available to Common Shares	$ 0.59	$ 0.78	$ 10.36	$ 1.27
Income from continuing operations available to Units	$ 226,812	$ 296,827	$ 3,957,263	$ 482,573
Numerator for net income per Unit – basic and diluted	$ 226,847	$ 296,941	$ 3,957,141	$ 482,842
Denominator for net income per Unit – basic	378,934	377,063	378,612	376,880
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