Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator for basic and diluted earnings per share:
Income from continuing operations attributable to common stockholders									$ 650,153	$ 406,740	$ 376,032
Discontinued operations	$ (167)	$ (118)	$ (148)	$ (489)	$ (2,331)	$ (22,383)	$ 18,243	$ 17,574	(922)	11,103	99,735
Net income attributable to common stockholders	$ 207,637	$ 149,452	$ 143,162	$ 148,980	$ 124,728	$ 22,852	$ 149,821	$ 120,442	$ 649,231	$ 417,843	$ 475,767
Denominator:
Denominator for basic earnings per share - weighted average shares (in shares)									344,703	330,311	294,175
Effect of dilutive securities:
Stock options (in shares)									569	360	495
Restricted stock awards (in shares)									176	41	55
OP units (in shares)									2,942	3,295	1,952
Denominator for diluted earnings per share - adjusted weighted average shares (in shares)									348,390	334,007	296,677
Basic earnings per share:
Income from continuing operations attributable to common stockholders (USD per share)	$ 0.59	$ 0.43	$ 0.42	$ 0.44	$ 0.38	$ 0.14	$ 0.39	$ 0.32	$ 1.88	$ 1.23	$ 1.28
Discontinued operations (USD per share)	0.00	0.00	0.00	0.00	(0.01)	(0.07)	0.06	0.05	0.00	0.03	0.34
Net income attributable to common stockholders (USD per share)	0.59	0.43	0.42	0.44	0.37	0.07	0.45	0.37	1.88	1.26	1.62
Diluted earnings per share:
Income from continuing operations attributable to common stockholders (USD per share)	0.58	0.42	0.42	0.44	0.38	0.14	0.40	0.32	1.86	1.22	1.26
Discontinued operations (USD per share)	0.00	0.00	0.00	0.00	(0.01)	(0.07)	0.05	0.05	0.00	0.03	0.34
Net income attributable to common stockholders (USD per share)	$ 0.58	$ 0.42	$ 0.42	$ 0.44	$ 0.37	$ 0.07	$ 0.45	$ 0.37	$ 1.86	$ 1.25	$ 1.60
Anti-dilutive options outstanding (in shares)									1,400	900	500