Stockholders' Equity - Summary of Option Activity under 2013 Plan and 2010 Plan (Details) $ / shares in Units, $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2018 $ / shares shares
Options
Number of Shares, Options outstanding at beginning of period | shares	781,725
Number of Shares, Options Granted | shares	563,150
Number of Shares, Options Exercised | shares	(7,813)
Number of Shares, Options Cancelled/forfeited | shares	(353,556)
Number of Shares, Options outstanding at end of period | shares	983,506	781,725
Number of Shares, Options exercisable at end of period | shares	314,635
Weighted Average Exercise Price, Options
Weighted Average Exercise Price, Options outstanding at beginning of period | $ / shares	$ 16.34
Weighted Average Exercise Price, Options Granted | $ / shares	23.10
Weighted Average Exercise Price, Options Exercised | $ / shares	11.81
Weighted Average Exercise Price, Options Cancelled/forfeited | $ / shares	23.51
Weighted Average Exercise Price, Options outstanding at end of period | $ / shares	17.42	$ 16.34
Weighted Average Exercise Price, Options exercisable at end of period | $ / shares	$ 11.62
Weighted Average Remaining Contract Term, Options
Weighted Average Remaining Contractual Term, Options outstanding at beginning of period	8 years	9 years
Weighted Average Remaining Contractual Term, Options exercisable at end of period	7 years 2 months 12 days
Aggregate Intrinsic Value, Options outstanding at end of period | $	$ 0.1
Aggregate Intrinsic Value, Options excersiable at end of period | $	$ 0.1