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		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net income	$ 277,846	$ 223,846	$ 708,402	$ 562,804
Net (income) loss attributable to Noncontrolling Interests – Partially Owned Properties	$ (830)	$ (750)	$ (2,450)	$ (1,939)
Dilutive Securities Options	3,187	2,972	3,035	2,642
Denominator for net income per share – diluted	386,896	383,884	386,177	383,433
Net income per Unit – basic	$ 0.72	$ 0.58	$ 1.83	$ 1.46
Net income per Unit – diluted	$ 0.71	$ 0.58	$ 1.82	$ 1.46
ERPOP [Member]
Net income	$ 277,846	$ 223,846	$ 708,402	$ 562,804
Net (income) loss attributable to Noncontrolling Interests – Partially Owned Properties	(830)	(750)	(2,450)	(1,939)
Allocation to Preference Units	(773)	(773)	(2,318)	(2,318)
Numerator for net income per Unit – basic and diluted	$ 276,243	$ 222,323	$ 703,634	$ 558,547
Denominator for net income per Unit – basic	383,709	380,912	383,142	380,791
Dilutive Securities Options	3,187	2,972	3,035	2,642
Denominator for net income per share – diluted	386,896	383,884	386,177	383,433
Net income per Unit – basic	$ 0.72	$ 0.58	$ 1.83	$ 1.46
Net income per Unit – diluted	$ 0.71	$ 0.58	$ 1.82	$ 1.46