Stock-Based Compensation - Summary of the Company's Stock Option Activity (Details) - Stock Options - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Shares
Options outstanding at the beginning of the period (in shares)	965,900	1,397,571
Granted (in shares)	273,800	439,741	151,827
Exercised (in shares)	(258,699)	(712,514)
Canceled (in shares)	(26,536)	(61,056)
Options outstanding at the end of the period (in shares)	876,365	965,900	1,397,571
Forfeited (in shares)	(78,100)	(97,842)
Options exercisable (in shares)	372,206
Forfeited (in shares)	(78,100)	(97,842)
Weighted Average Exercise Price
Options outstanding at the beginning of the period (in dollars per share)	$ 17.76	$ 15.51
Granted (in dollars per share)	25.68	17.20
Exercised (in dollars per share)	19.86	13.09
Options canceled weighted average cost (in dollars per share)	27.29	18.68
Options outstanding at the end of the period (in dollars per share)	19.13	17.76	$ 15.51
Options forfeited weighted average cost (in dollars per share)	20.16	16.38
Options exercisable (in dollars per share)	15.97
Options forfeited weighted average cost (in dollars per share)	$ 20.16	$ 16.38
Aggregate Intrinsic Value
Options outstanding (in dollars)	$ 17.8
Options exercisable (in dollars)	$ 8.7