Loans - Consumer Banking: Net Charge-Offs (Detail) (Consumer Banking, USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Net charge-offs	$ 190	$ 170	$ 460	$ 423
Percentage annualized net charge-off by average loans held for investment	1.07%	0.95%	0.87%	0.77%
Auto
Financing Receivable, Allowance for Credit Losses [Line Items]
Net charge-offs	176	152	421	366
Percentage annualized net charge-off by average loans held for investment	1.98%	2.01%	1.65%	1.69%
Home loan
Financing Receivable, Allowance for Credit Losses [Line Items]
Net charge-offs	2	5	12	13
Percentage annualized net charge-off by average loans held for investment	0.02%	0.06%	0.05%	0.04%
Retail banking
Financing Receivable, Allowance for Credit Losses [Line Items]
Net charge-offs	$ 12	$ 13	$ 27	$ 44
Percentage annualized net charge-off by average loans held for investment	1.36%	1.38%	1.00%	1.58%