Derivative Financial Instruments - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2012
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Managing interest rate risk for senior notes and subordinated notes	To manage interest rate risk for our 5.70% Senior Notes and 6.05% Subordinated Notes, we entered into fixed-for-floating interest rate swap agreements at the time of debt issuance based upon LIBOR with matched-terms.
Foreign Exchange Forward And Option Contracts | General maturity | Upper Limit
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Contract term	1 year
Foreign Exchange Forward And Option Contracts | Extended maturity | Upper Limit
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Contract term	5 years