Loans - TDR - Subsequent Defaults of Completed TDR Modifications (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 Contract	Dec. 31, 2013 Contract	Dec. 31, 2012 Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts	85,799	99,273	96,370
Total Loans	$ 271	$ 333	$ 336
Credit Card
Financing Receivable, Modifications [Line Items]
Number of Contracts	79,009	89,547	91,766
Total Loans	169	210	249
Credit Card | Domestic
Financing Receivable, Modifications [Line Items]
Number of Contracts	40,814	41,859	43,103
Total Loans	63	72	85
Credit Card | International
Financing Receivable, Modifications [Line Items]
Number of Contracts	38,195	47,688	48,663
Total Loans	106	138	164
Consumer Banking
Financing Receivable, Modifications [Line Items]
Number of Contracts	6,750	9,684	4,570
Total Loans	87	78	57
Consumer Banking | Auto
Financing Receivable, Modifications [Line Items]
Number of Contracts	6,651	9,525	4,364
Total Loans	72	68	39
Consumer Banking | Home loan
Financing Receivable, Modifications [Line Items]
Number of Contracts	24	33	99
Total Loans	5	3	7
Consumer Banking | Retail banking
Financing Receivable, Modifications [Line Items]
Number of Contracts	75	126	107
Total Loans	10	7	11
Commercial Banking
Financing Receivable, Modifications [Line Items]
Number of Contracts	40	42	34
Total Loans	15	45	30
Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
Number of Contracts	7	38	31
Total Loans	12	45	28
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
Number of Contracts	5	14	8
Total Loans	11	23	10
Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Number of Contracts	2	24	23
Total Loans	1	22	18
Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Contracts	33	4	3
Total Loans	$ 3	$ 0	$ 2