Summary of Significant Accounting Policies - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net income	$ 45,918	$ 17,916	$ 51,262	$ 38,455	$ 63,834	$ 89,717
Income from consolidated joint venture attributable to noncontrolling interest	(1,955)		(2,374)		(3,554)	(4,813)
Preferred stock dividends	(3,207)		(3,207)		(6,414)	(6,414)
Distributions paid on unvested restricted stock compensation	(61)		(59)		(122)	(118)
Undistributed income allocated to unvested restricted stock compensation	(156)		(179)		(167)	(298)
Numerator for basic and diluted income attributable to common stockholders	$ 40,539		$ 45,443		$ 53,577	$ 78,074
Denominator:
Weighted average basic and diluted common shares outstanding (in shares)	227,389		225,232		227,305	224,760
Basic and diluted income attributable to common stockholders per common share (in dollars per share)	$ 0.18		$ 0.20		$ 0.24	$ 0.35