Derivative Financial Instruments - Additional Information (Detail) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Net gain (loss) on derivative financial instruments	$ 3,588,000	$ 3,089,000
Net deferred gains expected to be reclassified out of AOCI over the next 12 months	1,300,000
Notional value of outstanding derivative contracts	1,300,000,000
Notional value of foreign currency forward-exchange contracts, maturity date	2017
Notional value of foreign currency forward-exchange contracts	870,000,000
Fair value of foreign currency forward-exchange contracts in net asset position	$ 7,300,000