Selected Quarterly Financial Data (Unaudited) - Quarterly Financial Information for Interim Periods Subsequent to IPO Closing (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended											12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	[1]	Jun. 30, 2014	[1]	Mar. 31, 2014	[1]	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 3,227	$ 4,294	$ 4,046	$ 4,010	$ 4,878	$ 13,193		$ 5,298		$ 5,001		$ 15,577	$ 28,370	$ 27,356
Income (loss) from operations	(2,603)	(820)	199	(6,137)	35	8,661		$ 1,378		$ 1,032		(9,361)	11,106	9,712
Net income (loss) attributable to common shareholders	$ (3,937)	$ (3,827)	$ 1,168	$ (9,156)	$ 1,224	$ 3,595						$ (15,752)	$ 13,018	$ 3,833
Basic net income (loss) per common share	$ (0.27)	$ (0.27)	$ 0.08	$ (0.64)	$ 0.14	$ 2.67						$ (1.10)	$ 4.11	$ 2.87
Diluted net income (loss) per common share	$ (0.27)	$ (0.27)	$ (0.07)	$ (0.64)	$ 0.13	$ 1.69						$ (1.10)	$ 3.28	$ 1.91

[1] The financial data, including per share amounts, for all interim periods prior to and including the three month period ended September 30, 2014, do not reflect the IPO.