Basis of Presentation and Significant Accounting Policies - Supplemental cash flow information (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended			12 Months Ended
	Oct. 31, 2014	Oct. 31, 2013	Feb. 29, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital expenditures financed by accounts payable				$ 434	$ 1,219	$ 479
Capital lease obligations				873	21	1,009
Cash paid during the year for:
Interest				32,278	33,266	34,051
Income taxes				1,800	2,417	5,557
Cash received during the year for:
Income tax refunds	$ 1,500	$ 2,590	$ 2,025	$ 2,284	$ 3,015	$ 3,184