Stock-Based Compensation - Summary of Common Stock Option Activity (Details) - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Number of Shares
Options outstanding at December 31 (shares)	821,470	826,498
Options granted (shares)	249,283	0
Options exercised (shares)	0	0
Options forfeited (shares)	0	(5,028)
Options outstanding at March 31 (shares)	1,070,753	821,470
Options exercisable at March 31 (shares)	821,470	821,470
Weighted-Average Exercise Price per share
Options outstanding at December 31 (in dollars per share)	$ 11.00	$ 11.00
Options granted (in dollars per share)	5.76	0.00
Options exercised (in dollars per share)	0.00	0.00
Options forfeited (in dollars per share)	0.00	11.00
Options outstanding at March 31 (in dollars per share)	9.78	11.00
Options exercisable at March 31 (in dollars per share)	$ 11.00	$ 11.00