Derivatives and Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended					9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Foreign Exchange Forward [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member]	Sep. 30, 2013 Nickel Futures or Option Contracts [Member] T	Dec. 31, 2012 Nickel Futures or Option Contracts [Member] T	Sep. 30, 2013 Hot Roll Steel Coil Option [Member] T	Dec. 31, 2012 Hot Roll Steel Coil Option [Member] T	Sep. 30, 2013 Aluminum Price Swaps [Member] T	Dec. 31, 2012 Aluminum Price Swaps [Member] T
Derivatives, Fair Value [Line Items]
Notional amount of foreign currency exchange contracts				$ 1.7	$ 0.7
Commodity notional value						173	182	1,300	1,300	50	80
Contract term for exchange contracts, Minimum	3 months
Contract term for exchange contracts, Maximum	12 months
Assets held for sale	4.5		3.6
Impairment charge of asset held for sale	$ 2.0	$ 0.9