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	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income (loss) from continuing operations	$ 628,381	$ 4,479,586	$ 907,621
Partially Owned Properties	(2,323)	(16,430)	(3,657)
Premium on redemption of Preferred Shares	0	0	(3,486)
Discontinued operations, net	$ 0	$ 518	$ 397
Dilutive Securities Options	2,809	3,163	3,546
Weighted average Common Shares outstanding	382,678	381,992	380,620
Net income available to Common Shares	$ 1.64	$ 11.75	$ 2.37
Net income available to Common Shares	1.63	11.68	2.36
Income from continuing operations available to Common Shares	1.64	11.75	2.37
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0	0	0
Income from continuing operations available to Common Shares	1.63	11.68	2.36
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	$ 0	$ 0	$ 0
ERPOP [Member]
Income (loss) from continuing operations	$ 628,381	$ 4,479,586	$ 907,621
Partially Owned Properties	(2,323)	(16,430)	(3,657)
Allocation to Preference Units	(3,091)	(3,091)	(3,357)
Premium on redemption of Preferred Shares	0	0	(3,486)
Income Loss From Continuing Operations Available To Units	622,967	4,460,065	897,121
Discontinued operations, net	0	518	397
Numerator for net income per Unit – basic and diluted	$ 622,967	$ 4,460,583	$ 897,518
Weighted Average Limited Partnership and General Partnership Units Outstanding, Basic	379,869	378,829	377,074
Dilutive Securities Options	2,809	3,163	3,546
Weighted average Common Shares outstanding	382,678	381,992	380,620
Net income available to Common Shares	$ 1.64	$ 11.75	$ 2.37
Net income available to Common Shares	1.63	11.68	2.36
Income from continuing operations available to Common Shares	1.64	11.75	2.37
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0	0	0
Income from continuing operations available to Common Shares	1.63	11.68	2.36
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	$ 0	$ 0	$ 0