Earnings 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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net income	$ 321,299	$ 118,410	$ 430,556	$ 338,958
Net (income) loss attributable to Noncontrolling Interests – Partially Owned Properties	$ (821)	$ (509)	$ (1,620)	$ (1,189)
Dilutive Securities Options	2,880	2,628	2,790	2,495
Denominator for net income per share – diluted	386,107	383,423	385,644	383,224
Net income per Unit – basic	$ 0.83	$ 0.31	$ 1.11	$ 0.88
Net income per Unit – diluted	$ 0.83	$ 0.31	$ 1.11	$ 0.88
ERPOP [Member]
Net income	$ 321,299	$ 118,410	$ 430,556	$ 338,958
Net (income) loss attributable to Noncontrolling Interests – Partially Owned Properties	(821)	(509)	(1,620)	(1,189)
Allocation to Preference Units	(772)	(772)	(1,545)	(1,545)
Numerator for net income per Unit – basic and diluted	$ 319,706	$ 117,129	$ 427,391	$ 336,224
Denominator for net income per Unit – basic	383,227	380,795	382,854	380,729
Dilutive Securities Options	2,880	2,628	2,790	2,495
Denominator for net income per share – diluted	386,107	383,423	385,644	383,224
Net income per Unit – basic	$ 0.83	$ 0.31	$ 1.11	$ 0.88
Net income per Unit – diluted	$ 0.83	$ 0.31	$ 1.11	$ 0.88