Prepaid Expenses and Other Current Assets - Components of Prepaid Expenses and Other Current Assets (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Collateral on deposit-commodity derivative contracts	$ 267	$ 767
Commodity derivative contracts	458	548
Deferred expense	12,003
Loss fund payments-workers' compensation	6,883	6,968
Prepaid insurance	2,131	1,261
Prepaid tooling	1,604	764
Other	1,746	1,833
Total prepaid expenses and other current assets	$ 25,092	$ 12,141