Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Data [Abstract]
Revenues	$ 160,184	$ 167,411	$ 176,032	$ 174,777	$ 103,656	$ 106,102	$ 108,085	$ 108,717	$ 678,404	$ 426,560	$ 316,532
Net income (loss) available for common shareholders	$ 65,029	$ (3,939)	$ (64,774)	$ 34,019	$ (57,695)	$ (449)	$ 29,602	$ 6,287	$ 30,335	$ (22,255)	$ 11,815
Net income (loss) available for common shareholders per common share (basic and diluted) (in dollars per share)	$ 1.35	$ (0.08)	$ (1.35)	$ 0.71	$ (2.31)	$ (0.02)	$ 1.20	$ 0.25	$ 0.63	$ (0.90)	$ 0.56
Common distributions declared (in dollars per share)	$ 0.55	$ 0.55	$ 0.55	$ 0.55	$ 1.72	$ 1.72	$ 1.72	$ 1.72