Earnings 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	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Income from continuing operations	$ 685,192	$ 628,381	$ 4,479,586
Allocation to Noncontrolling Interests – Operating Partnership, net	(24,939)	(22,604)	(171,491)
Partially Owned Properties	(2,718)	(2,323)	(16,430)
Preferred distributions	(3,090)	(3,091)	(3,091)
Income from continuing operations available to Common Shares, net of Noncontrolling Interests	654,445	600,363	4,288,574
Discontinued operations, net of Noncontrolling Interests			498
Net income available to Common Shares	654,445	600,363	4,289,072
Income from continuing operations available to Common Shares	679,384	622,967	4,460,065
Discontinued operations, net	0	0	518
Numerator for net income per share – diluted	$ 679,384	$ 622,967	$ 4,460,583
Weighted average Common Shares outstanding	368,052	366,968	365,002
OP Units	12,869	12,901	13,827
Dilutive Securities Options	2,774	2,809	3,163
Denominator for net income per share – diluted	383,695	382,678	381,992
Net income available to Common Shares	$ 1.78	$ 1.64	$ 11.75
Net income available to Common Shares	1.77	1.63	11.68
Income from continuing operations available to Common Shares	1.78	1.64	11.75
Net income available to Units	1.78	1.64	11.75
Income from continuing operations available to Common Shares	1.77	1.63	11.68
Net income available to Units	1.77	1.63	11.68
Distributions declared per Common Share outstanding	$ 2.16	$ 2.015	$ 13.015