Derivative Financial Instruments - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
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 London Interbank Offered Rates (“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
3.875% Convertible Notes
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Convertible notes initial conversion price before hedge and warrant agreement	53.04
3.875% Convertible Notes | Hedge and warrant agreement
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Convertible note hedge and warrant agreement cost	20.6
Price per share of the conversion feature for the hedge and warrant agreement associated with our convertible notes	64.43
Period of warrants ratable expiration beginning July 15, 2011	60 days