Quarterly Financial Information (unaudited) (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
Quarterly Financial Information Disclosure [Abstract]
Gross revenues	$ 87,741	$ 83,666	$ 86,651	$ 92,892	$ 81,829	$ 77,371	$ 69,502	$ 62,615	$ 350,950	$ 291,317	$ 254,767
Net revenue	42,098	32,754	42,302	35,435	16,260	32,333	28,857	31,456	152,589	108,906	159,660
Net income (loss)	4,358	(4,532)	(2,569)	(11,602)	(36,460)	(17,173)	(18,708)	(13,141)	$ (14,345)	$ (85,482)	$ (2,231)
Net loss attributable to common stockholders	$ 5,096	$ (4,074)	$ (1,498)	$ (11,058)	$ (35,857)	$ (16,634)	$ (17,895)	$ (12,573)
Basic (in dollars per share)	$ 0.07	$ (0.06)	$ (0.02)	$ (0.15)	$ (0.50)	$ (0.23)	$ (0.25)	$ (0.18)
Diluted (in dollars per share)	$ 0.07	$ (0.06)	$ (0.02)	$ (0.15)	$ (0.50)	$ (0.23)	$ (0.25)	$ (0.18)