Financing Arrangements - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012
Line of Credit Facility [Line Items]
Credit facility maximum borrowing capacity	$ 1,500,000,000
Credit facility, maturity date	Jun. 30, 2016
Credit facility interest rate above LIBOR	1.25%
Line of credit facility fee	0.25%
Uncommitted Credit Facility
Line of Credit Facility [Line Items]
Credit facility maximum borrowing capacity	$ 320,000,000