Earning Per Share and Earnings Per Unit - Computation of Net Income per Unit Basic and Net Income per Unit Diluted for Operating Partnership (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income (loss) from continuing operations	$ 204,160	$ 228,365	$ 354,101	$ 3,960,353
Net (income) attributable to Noncontrolling Interests – Partially Owned Properties	(765)	(781)	(1,553)	(1,545)
Discontinued operations, net	$ 0	$ 35	$ 0	$ (122)
Weighted average Common Shares outstanding	382,692	382,065	382,505	382,012
Net income available to Common Shares	$ 0.53	$ 0.60	$ 0.92	$ 10.43
Net income available to Common Shares	0.53	0.59	0.92	10.36
Income from continuing operations available to Common Shares	0.53	0.60	0.92	10.43
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0	0	0	0
Income from continuing operations available to Common Shares	0.53	0.59	0.92	10.36
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	$ 0	$ 0	$ 0	$ 0
ERPOP [Member]
Income (loss) from continuing operations	$ 204,160	$ 228,365	$ 354,101	$ 3,960,353
Net (income) attributable to Noncontrolling Interests – Partially Owned Properties	(765)	(781)	(1,553)	(1,545)
Allocation to Preference Units	(773)	(772)	(1,546)	(1,545)
Income Loss From Continuing Operations Available To Units	202,622	226,812	351,002	3,957,263
Discontinued operations, net	0	35	0	(122)
Numerator for net income per Unit – basic and diluted	$ 202,622	$ 226,847	$ 351,002	$ 3,957,141
Weighted Average Limited Partnership and General Partnership Units Outstanding, Basic	379,733	378,934	379,619	378,612
Dilutive Securities Options	2,959	3,131	2,886	3,400
Weighted average Common Shares outstanding	382,692	382,065	382,505	382,012
Net income available to Common Shares	$ 0.53	$ 0.60	$ 0.92	$ 10.43
Net income available to Common Shares	0.53	0.59	0.92	10.36
Income from continuing operations available to Common Shares	0.53	0.60	0.92	10.43
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0	0	0	0
Income from continuing operations available to Common Shares	0.53	0.59	0.92	10.36
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	$ 0	$ 0	$ 0	$ 0