Joint Venture - Operating Results (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Schedule of Equity Method Investments [Line Items]
Net sales	$ 273,410	$ 329,392	$ 566,124	$ 692,308
Cost of materials	201,461	240,681	420,892	504,648
Income (loss) before taxes	(11,614)	(3,619)	(23,605)	(3,546)
Net (loss) income	(3,799)	(2,978)	(14,421)	(7,278)
Joint venture
Schedule of Equity Method Investments [Line Items]
Net sales	57,451	67,662	114,780	144,467
Cost of materials	48,152	56,267	96,371	119,665
Income (loss) before taxes	3,695	4,433	7,051	11,534
Net (loss) income	$ 2,988	$ 3,466	$ 5,926	$ 9,482