Stock-Based Compensation - Summary of Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Option Shares
Outstanding at beginning of period (in shares)	58,411
Replacement stock options (in shares)	0
Granted (in shares)	0	0	0
Exercised (in shares)	(4,950)	(5,784)	(42,680)
Forfeited (in shares)	(578)
Expired (in shares)	(1,898)
Outstanding at end of period (in shares)	50,985	58,411
Exercisable at end of period (in shares)	50,985
Weighted Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 24.37
Replacement stock options (in dollars per share)	0.00
Granted (in dollars per share)	0.00
Exercised (in dollars per share)	22.93
Forfeited (in dollars per share)	23.33
Expired (in dollars per share)	36.08
Outstanding at end of period (in dollars per share)	24.09	$ 24.37
Exercisable at end of period (in dollars per share)	$ 24.09
Weighted Average Remaining Contractual Term
Outstanding at end of period	8 months 45 days
Exercisable at end of period	8 months 45 days
Aggregate Intrinsic Value
Outstanding at end of period	$ 725
Exercisable at end of period	$ 725