Earnings Per Share ("EPS") (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator
Net Income									$ 161,673	$ 554,839	$ 522,912
Net income attributable to noncontrolling interests									(15,543)	(37,844)	(35,350)
Net income attributable to the Company	$ 32,751	$ 17,498	$ 26,638	$ 69,243	$ 37,128	$ 13,730	$ 45,222	$ 420,915	146,130	516,995	487,562
Allocation of earnings to participating securities									(757)	(779)	(1,493)
Numerator for basic and diluted EPS—net income attributable to common stockholders									$ 145,373	$ 516,216	$ 486,069
Denominator
Denominator for basic EPS—weighted average number of common shares outstanding (shares)									141,877,000	146,599,000	157,916,000
Effect of dilutive securities
Share and unit based compensation (shares)									36,000	112,000	144,000
Denominator for diluted EPS—weighted average number of common shares outstanding (shares)									141,913,000	146,711,000	158,060,000
EPS—net income attributable to common stockholders:
Basic (dollars per share)	$ 0.23	$ 0.12	$ 0.19	$ 0.48	$ 0.26	$ 0.09	$ 0.31	$ 2.77	$ 1.02	$ 3.52	$ 3.08
Diluted (dollars per share)	$ 0.23	$ 0.12	$ 0.19	$ 0.48	$ 0.26	$ 0.09	$ 0.31	$ 2.76	$ 1.02	$ 3.52	$ 3.08
Convertible preferred units
Antidilutive securities
Antidilutive securities (shares)									90,619	133,366	139,186
Partnership unit
Antidilutive securities
Antidilutive securities (shares)									10,416,321	10,721,271	10,562,154