Stock-Based Compensation - Components of Stock-Based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Total stock-based compensation expense	$ 1,389	$ 1,991	$ 1,809
Tax benefit of stock-based compensation expense	0	0	(696)
After-tax effect of stock based compensation	1,389	1,991	1,113
Stock options
Total stock-based compensation expense	120	90	194
Restricted stock units
Total stock-based compensation expense	$ 1,269	$ 1,901	$ 1,615