Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Accrued expenses
Salaries and benefits	$ 8,093	$ 11,662
Interest	1,391	2,583
Other taxes	949	1,048
Accrued expenses	10,433	15,293
Other current liabilities
Other postretirement benefits, current	3,465	3,332
Installment financing contracts, current	2,664	2,157
Other	693	838
Other current liabilities	$ 6,822	$ 6,327