Joint Venture - Operating Results (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Schedule of Equity Method Investments [Line Items]
Net sales	$ 253,410	$ 292,714
Cost of materials	188,531	219,431
Income (loss) before taxes	(16,049)	(11,991)
Net (loss) income	(15,998)	(10,622)
Joint venture
Schedule of Equity Method Investments [Line Items]
Net sales	65,251	57,329
Cost of materials	54,303	48,219
Income (loss) before taxes	4,804	3,356
Net (loss) income	$ 3,814	$ 2,938