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
	Mar. 31, 2019	Mar. 31, 2018
Net income	$ 109,257	$ 220,548
Partially Owned Properties	$ (799)	$ (680)
Dilutive Securities Options	2,707	2,355
Denominator for net income per share – diluted	385,184	383,018
Net income available to Common Shares	$ 0.28	$ 0.57
Net income available to Common Shares	$ 0.28	$ 0.57
ERPOP [Member]
Net income	$ 109,257	$ 220,548
Partially Owned Properties	(799)	(680)
Allocation to Preference Units	(773)	(773)
Numerator for net income per Unit – basic and diluted	$ 107,685	$ 219,095
Denominator for net income per Unit – basic	382,477	380,663
Dilutive Securities Options	2,707	2,355
Denominator for net income per share – diluted	385,184	383,018
Net income available to Common Shares	$ 0.28	$ 0.57
Net income available to Common Shares	$ 0.28	$ 0.57