Earning Per Share and Earnings Per Unit - Computation of Net Income per Share Basic and Net Income per Share Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net income	$ 220,548	$ 149,941
Allocation to Noncontrolling Interests – Operating Partnership	(8,059)	(5,411)
Partially Owned Properties	(680)	(788)
Preferred distributions	(773)	(773)
Net income available to Common Shares	211,036	142,969
Numerator for net income per share – diluted	$ 219,095	$ 148,380
Weighted average Common Shares outstanding	367,800	366,605
Dilutive Op Units	12,863	12,899
Dilutive Securities Options	2,355	2,776
Weighted average Common Shares outstanding	383,018	382,280
Net income available to Common Shares	$ 0.57	$ 0.39
Net income available to Common Shares	$ 0.57	$ 0.39