Stockholders' Equity - Summary of Option Activity under 2013 Plan and 2010 Plan (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Options
Number of Shares, Options outstanding at beginning of period	463,600
Number of Shares, Options granted	287,500
Number of Shares, Options outstanding at end of period	751,100	463,600
Number of Shares, Options exercisable at end of period	170,947
Weighted Average Exercise Price, Options
Weighted Average Exercise Price, Options outstanding at beginning of period	$ 11.23
Weighted Average Exercise Price, Options granted	21.13
Weighted Average Exercise Price, Options outstanding at end of period	15.02	$ 11.23
Weighted Average Exercise Price, Options exercisable at end of period	$ 4.32
Weighted Average Remaining Contract Term, Options
Weighted Average Remaining Contractual Term, Options outstanding at beginning of period	9 years	9 years 6 months
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	$ 11.9
Aggregate Intrinsic Value, Options excersiable at end of period	$ 4.5