Subsequent Events (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012
Subsequent Event [Line Items]
Carry Value Of Loans Leases Or Lines Of Credit Securitized	$ 509
Treasury Stock, Value, Acquired, Cost Method		(1,320)	(650)
Subsequent event
Subsequent Event [Line Items]
Carry Value Of Loans Leases Or Lines Of Credit Securitized		1,300
Stock redeemed or called during period, shares		3,950,705
Treasury Stock, Value, Acquired, Cost Method		$ 99
Repurchase Shares Authorized		100,000,000
Automobile Loan Transfer Date		Feb. 20, 2014
Accelerated Share Repurchase Date		Jan. 28, 2014
Expected Settlement Date		Mar. 26, 2014