Stock-Based Compensation - Summary of Stock Option Activity (Details) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares
Stock-based compensation
Options Available for Grant, Outstanding, Beginning balance	83,929
Options Available for Grant, Options authorized	1,084,516
Options Available for Grant, RSUs granted	(60,450)
Options Available for Grant, RSUs cancelled/forfeited	1,900
Options Available for Grant, Options granted	(310,715)
Options Available for Grant, Options cancelled/forfeited	28,834.00
Options Available for Grant, Outstanding, Ending balance	826,988	83,929
Number of Options, Outstanding, Beginning balance	1,593,195
Number of Options, Options granted	310,715
Number of Options, Options exercised	(190,800)
Number of Options, Options cancelled/forfeited	(30,707)
Number of Options, Outstanding, Ending balance	1,696,187	1,593,195
Number of Options, exercisable	746,702
Weighted - Average Exercise Price Per Share, Options outstanding, Beginning balance | $ / shares	$ 8.88
Weighted - Average Exercise Price Per Share, Options granted | $ / shares	8.79
Weighted - Average Exercise Price Per Share, Options exercised | $ / shares	4.69
Weighted - Average Exercise Price Per Share, Options cancelled/forfeited | $ / shares	7.97
Weighted - Average Exercise Price Per Share, Options outstanding, Ending balance | $ / shares	7.28	$ 8.88
Weighted - Average Exercise Price Per Share, Options exercisable | $ / shares	$ 5.85
Weighted - Average Remaining Contractual Life, Options outstanding	7 years 2 months 12 days	6 years 7 months 6 days
Weighted - Average Remaining Contractual Life, Options exercisable	4 years 9 months 18 days
Aggregate Intrinsic Value, Options outstanding | $	$ 3,204	$ 1,997
Aggregate Intrinsic Value, Options exercised | $	815
Aggregate Intrinsic Value, Options exercisable | $	$ 2,355
Adjustment
Stock-based compensation
Options Available for Grant, Outstanding, Beginning balance	(1,026)
Options Available for Grant, Outstanding, Ending balance		(1,026)
Number of Options, Outstanding, Beginning balance	13,784
Number of Options, Outstanding, Ending balance		13,784
Weighted - Average Exercise Price Per Share, Options outstanding, Beginning balance | $ / shares	$ 4.54
Weighted - Average Exercise Price Per Share, Options outstanding, Ending balance | $ / shares		$ 4.54