Summary of Quarterly Financial Information (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	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, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 151,399	$ 146,575	$ 141,030	$ 170,224	$ 194,933	$ 192,873	$ 176,244	$ 167,293	$ 199,309	$ 186,402	$ 178,529	$ 167,271	$ 609,228	$ 731,343	$ 731,511
Operating income	19,426	11,928	334	26,973	47,112	45,279	36,239	26,076	58,490	48,538	49,665	34,164	58,661	154,706	190,857
Net income (loss)	710	(12,269)	(19,618)	8,288	28,720	26,784	18,930	9,856	39,781	29,230	30,184	18,058	$ (22,889)	$ 84,290	$ 117,253
Net income (loss) attributable to common stockholders	$ (210)	$ (8,204)	$ (12,793)	$ 4,495	$ 16,799	$ 15,882	$ 11,087	$ 5,677	$ 22,842	$ 16,342	$ 16,651	$ 9,768
Basic and diluted net income per share attributable to common stockholders (USD per share)	$ 0.00	$ (0.05)	$ (0.07)	$ 0.02	$ 0.09	$ 0.09	$ 0.06	$ 0.03	$ 0.13	$ 0.10	$ 0.10	$ 0.06