Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accrued expenses
Salaries and benefits	$ 11,662	$ 12,185
Interest	2,583	1,262
Other taxes	1,048	1,044
Accrued expenses	15,293	14,491
Other current liabilities
Other postretirement benefits, current	3,332	2,929
Installment financing contracts, current	2,157	1,849
Other	838	1,154
Other current liabilities	$ 6,327	$ 5,932