Financing Arrangements - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended
	May 31, 2013	Dec. 31, 2013
Line of Credit Facility [Line Items]
Credit facility maximum borrowing capacity	$ 1,500,000,000	$ 2,000,000,000
Credit facility, maturity date	Jun. 30, 2016	Jun. 30, 2017
Credit facility interest rate above LIBOR		1.25%
Line of credit facility fee		0.25%
Committed Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit facility borrowing capacity		350,000,000
Uncommitted Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit facility maximum borrowing capacity		$ 345,000,000