Employee Benefit Plans - Other Compensation Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Classification of liabilities in the Consolidated Balance Sheets
Current liabilities	$ 973	$ 967
Other long-term liabilities	3,327	3,583
Total liabilities	4,300	4,550
Plan expenses	1,300	1,000	$ 800
Accrued compensation
Classification of liabilities in the Consolidated Balance Sheets
Current liabilities	$ 973	$ 967