Stock-Based Compensation - Summary of Common Stock Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Shares
Options outstanding at December 31 (shares)	835,786	840,298	846,874
Options granted (shares)	0	0	0
Options exercised (shares)	(9,288)	0	(1,584)
Options forfeited (shares)	0	(4,512)	(4,992)
Options outstanding at December 31 (shares)	826,498	835,786	840,298
Options exercisable at December 31 (shares)	826,498	42,042	23,133
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)	11.00	0.00	11.00
Options forfeited (in dollars per share)	0.00	11.00	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