Joint Venture - Operating Results (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Schedule of Equity Method Investments [Line Items]
Net sales	$ 292,714	$ 362,916
Cost of materials	219,431	263,967
Income before taxes	(11,991)	73
Net (loss) income	(10,622)	(4,300)
Joint venture
Schedule of Equity Method Investments [Line Items]
Net sales	57,329	76,805
Cost of materials	48,219	63,398
Income before taxes	3,356	7,101
Net (loss) income	$ 2,938	$ 6,016