Income Taxes - Income Tax Expense Components (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ 12,995	$ 12,979	$ 14,797
State	3,243	3,514	2,669
Foreign	1,476	1,932	1,475
Total current	17,714	18,425	18,941
Deferred:
Federal	(9,425)	8,872	4,562
State	2,749	1,222	512
Foreign	72	(596)	216
Total deferred	(6,604)	9,498	5,290
Income tax expense	$ 11,110	$ 27,923	$ 24,231