Stock-Based Compensation - Summary of Common Stock Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Options outstanding at December 31 (shares)	826,498	835,786	840,298
Options granted (shares)	0	0	0
Options exercised (shares)	0	9,288	0
Options forfeited (shares)	(5,028)	0	(4,512)
Options outstanding at December 31 (shares)	821,470	826,498	835,786
Options exercisable at December 31 (shares)	821,470	826,498	42,042
Weighted-Average Exercise Price per share
Options outstanding at December 31 (in dollars per share)	$ 11.00	$ 11.00	$ 11.00
Options granted (in dollars per share)	0.00	0.00	0.00
Options exercised (in dollars per share)	0.00	11.00	0.00
Options forfeited (in dollars per share)	11.00	0.00	11.00
Options outstanding at December 31 (in dollars per share)	11.00	11.00	11.00
Options exercisable at December 31 (in dollars per share)	$ 11.00	$ 11.00	$ 11.00