Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Accrued expenses
Salaries and benefits	$ 9,765	$ 11,662
Interest	2,510	2,583
Other taxes	1,035	1,048
Accrued expenses	13,310	15,293
Other current liabilities
Other postretirement benefits, current	3,465	3,332
Installment financing contracts, current	1,720	2,157
Other	763	838
Other current liabilities	$ 5,948	$ 6,327