Summarized Quarterly Data (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
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Net revenues	$ 15,183	$ 18,713	$ 17,186	$ 14,769	$ 15,314	$ 18,530	$ 17,405	$ 16,205	$ 65,851	$ 67,454	$ 68,166
Loss from operations	(9,887)	(6,844)	(6,830)	(6,356)	(6,484)	(5,388)	(7,047)	(4,764)	(29,917)	(23,683)	(33,960)
Net loss	$ (12,105)	$ (10,872)	$ (11,916)	$ (11,451)	$ (6,587)	$ (5,388)	$ (7,045)	$ (5,177)	$ (46,344)	$ (24,197)	$ (36,610)
Loss per common share, basic (usd per share)	$ (0.39)	$ (0.35)	$ (0.39)	$ (0.37)	$ (0.19)	$ (0.18)	$ (0.23)	$ (0.26)	$ (1.50)	$ (0.86)	$ (3.42)
Loss per common share, diluted (usd per share)	$ (0.39)	$ (0.35)	$ (0.39)	$ (0.37)	$ (0.19)	$ (0.18)	$ (0.23)	$ (0.26)	$ (1.50)	$ (0.86)	$ (3.42)