Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Other Current Liabilities [Line Items]
Payroll and incentive compensation	$ 10,499	$ 11,432
Union dues and benefits	8,182	6,721
Profit sharing and thrift plan	1,294	4,760
Taxes, other than income taxes	3,578	3,709
Legal settlements	0	302
Other	5,303	4,816
Other current liabilities, total	$ 28,856	$ 31,740