Stock-Based Compensation Expense - Summary of Stock Option Activity Under Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding December 31, 2019	792,439
Shares, Granted	109,239
Shares, Exercised	0	0
Shares, Outstanding at March 31, 2020	901,678		792,439
Shares, Exercisable at March 31, 2020	438,822
Shares, Vested and expected to vest at March 31, 2020	901,678
Weighted Average Exercise Price, Outstanding December 31, 2019	$ 6.59
Weighted Average Exercise Price, Granted	8.63
Weighted Average Exercise Price, Outstanding at March 31, 2020	6.84		$ 6.59
Weighted Average Exercise Price, Exercisable at March 31, 2020	9.41
Weighted Average Exercise Price, Vested and expected to vest at March 31, 2020	$ 6.84
Outstanding, Weighted Average Remaining Contractual Life (in years)	7 years 4 months 24 days		7 years 3 months 18 days
Exercisable, Weighted Average Remaining Contractual Life (in years)	5 years 8 months 12 days
Vested and expected to vest, Weighted Average Remaining Contractual Life (in years)	7 years 4 months 24 days
Aggregate Intrinsic Value, Outstanding December 31, 2019	$ 3,366		$ 3,363
Aggregate Intrinsic Value, Exercisable at March 31, 2020	1,409
Aggregate Intrinsic Value, Vested and expected to vest at March 31, 2020	$ 3,366