Loans - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 67,710,000,000	$ 61,452,000,000	$ 67,710,000,000	$ 61,452,000,000	$ 63,258,000,000
Net deferred origination costs (Fees)	(10,000,000)		(10,000,000)		30,000,000
Net unamortized premium on loans	17,000,000		17,000,000		25,000,000
Amortized net premiums on loans	1,000,000	2,000,000	4,000,000	20,000,000
Total nonaccruing loans	1,360,000,000		1,360,000,000		1,629,000,000
Interest income that would have been recorded if the nonaccrual receivable had been current in accordance with contractual terms during the period	25,000,000		86,000,000
Interest income that was recorded on nonaccrual receivables included in interest income on nonaccrual loans during the period		37,000,000		92,000,000
Current interest income (expense) in finance loans	11,000,000	10,000,000	27,000,000	14,000,000
Commercial loans removed from TDR classification	11,000,000		11,000,000
Parent And Other Subsidiaries Of Common Parent [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	5,854,000,000		5,854,000,000		4,514,000,000
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	19,201,000,000		19,201,000,000		19,108,000,000
Total nonaccruing loans	$ 1,105,000,000		$ 1,105,000,000		$ 1,129,000,000
Weighted average rate of reduction	1.80%	1.90%	2.00%	1.80%