Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Selected Quarterly Financial Data (unaudited)
Total revenue	$ 27,313	$ 24,174	$ 22,418	$ 20,157	$ 19,761	$ 17,952	$ 16,824	$ 15,502	$ 94,062	$ 70,039	$ 48,428
Gross profit	9,374	6,991	6,296	6,224	5,842	5,675	4,820	4,574	28,885	20,911	10,616
Income (loss) from operations	(248)	1,706	1,479	1,614	2,007	1,533	1,772	853	4,551	6,165	107
Net income (loss) attributable to common stockholders:
Basic	(6,031)	1,228	(890)	293	1,504	(14,066)	(1,245)	(696)	(3,811)	(12,830)	(4,991)
Diluted	$ (6,031)	$ (803)	$ (890)	$ 94	$ 395	$ (14,066)	$ (1,245)	$ (696)	$ (6,889)	$ (12,830)	$ (4,991)
Net income (loss) per share attributable to common stockholders:
Basic (in dollars per share)	$ (0.39)	$ 0.25	$ (0.18)	$ 0.06	$ 0.33	$ (3.21)	$ (0.30)	$ (0.17)	$ (0.51)	$ (2.97)	$ (1.23)
Diluted (in dollars per share)	$ (0.39)	$ (0.08)	$ (0.18)	$ 0.01	$ 0.03	$ (3.21)	$ (0.30)	$ (0.17)	$ (0.59)	$ (2.97)	$ (1.23)