Stockholders' Equity - Summary of Option Activity under 2013 Plan and 2010 Plan (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Options
Number of Shares, Options outstanding at beginning of period	781,725
Number of Shares, Options Granted	430,150
Number of Shares, Options Cancelled/forfeited	(60,000)
Number of Shares, Options outstanding at end of period	1,151,875	781,725
Number of Shares, Options exercisable at end of period	251,135
Weighted Average Exercise Price, Options
Weighted Average Exercise Price, Options outstanding at beginning of period	$ 16.34
Weighted Average Exercise Price, Options Granted	28.15
Weighted Average Exercise Price, Options outstanding at end of period	18.77	$ 16.34
Weighted Average Exercise Price, Options exercisable at end of period	8.29
Weighted Average Exercise Price, Options Cancelled/forfeited	$ 22.18
Weighted Average Remaining Contract Term, Options
Weighted Average Remaining Contractual Term, Options outstanding at beginning of period	9 years 4 months 24 days	9 years
Weighted Average Remaining Contractual Term, Options exercisable at end of period	7 years 8 months 12 days
Aggregate Intrinsic Value, Options outstanding at end of period	$ 6.8
Aggregate Intrinsic Value, Options excersiable at end of period	$ 4.5