Loans - Loan Portfolio Composition and Aging Analysis (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	$ 222,480	$ 203,438
Past due	8,035	6,895
Loans held for investment	$ 245,586	$ 229,851	$ 208,316
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Financing Receivable, Percent Current	90.59%	88.51%
Total Delinquent Loans (as percent)	3.27%	3.00%
Total Loans (as percent)	100.00%	100.00%
Loans and Leases Receivable, Deferred Income	$ 558	$ 499
Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	101,394	92,857
Past due	4,156	3,268
Loans held for investment	105,552	96,125
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	55,190	48,528
Past due	3,408	3,284
Loans held for investment	73,054	70,372
Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	44,762	38,549
Past due	3,154	3,000
Loans held for investment	47,916	41,549
Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	6,951	6,465
Past due	205	235
Loans held for investment	21,584	25,227
Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	3,477	3,514
Past due	49	49
Loans held for investment	3,554	3,596
Commercial Banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	65,840	61,976
Past due	463	332
Loans held for investment	66,916	63,266
Commercial Banking | Total commercial lending
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	65,367	61,369
Past due	453	326
Loans held for investment	66,433	62,653
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	26,536	25,449
Past due	45	38
Loans held for investment	26,609	25,518
Commercial Banking | Commercial and industrial
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	38,831	35,920
Past due	408	288
Loans held for investment	39,824	37,135
Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	473	607
Past due	10	6
Loans held for investment	483	613
Other
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	56	77
Past due	8	11
Loans held for investment	64	88
Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	$ 15,071	$ 19,518
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Total Loans (as percent)	6.14%	8.49%
Receivables Acquired with Deteriorated Credit Quality [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	$ 2	$ 0
Receivables Acquired with Deteriorated Credit Quality [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	14,456	18,560
Receivables Acquired with Deteriorated Credit Quality [Member] | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	0	0
Receivables Acquired with Deteriorated Credit Quality [Member] | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	14,428	18,527
Receivables Acquired with Deteriorated Credit Quality [Member] | Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	28	33
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial Banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	613	958
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial Banking | Total commercial lending
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	613	958
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	28	31
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial Banking | Commercial and industrial
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	585	927
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	0	0
Receivables Acquired with Deteriorated Credit Quality [Member] | Other
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	0	0
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	$ 3,466	$ 3,069
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Total Delinquent Loans (as percent)	1.41%	1.33%
Financing Receivables, 30 to 59 Days Past Due [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	$ 1,277	$ 1,016
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	2,107	1,963
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	2,041	1,901
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	44	41
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	22	21
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	79	88
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Banking | Total commercial lending
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	72	85
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	45	34
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Banking | Commercial and industrial
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	27	51
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	7	3
Financing Receivables, 30 to 59 Days Past Due [Member] | Other
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	3	2
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	$ 1,920	$ 1,668
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Total Delinquent Loans (as percent)	0.78%	0.73%
Financing Receivables, 60 to 89 Days Past Due [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	$ 918	$ 725
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	917	906
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	890	880
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	20	18
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	7	8
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	85	35
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Banking | Total commercial lending
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	84	34
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Banking | Commercial and industrial
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	84	34
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	1	1
Financing Receivables, 60 to 89 Days Past Due [Member] | Other
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	0	2
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	$ 2,649	$ 2,158
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Total Delinquent Loans (as percent)	1.08%	0.94%
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	$ 1,961	$ 1,527
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	384	415
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	223	219
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	141	176
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	20	20
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	299	209
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Banking | Total commercial lending
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	297	207
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	0	4
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Banking | Commercial and industrial
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	297	203
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	2	2
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Other
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	5	7
Geographic Distribution, Domestic [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	93,279	84,954
Past due	3,839	2,985
Loans held for investment	97,120	87,939
Geographic Distribution, Domestic [Member] | Receivables Acquired with Deteriorated Credit Quality [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	2	0
Geographic Distribution, Domestic [Member] | Financing Receivables, 30 to 59 Days Past Due [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	1,153	906
Geographic Distribution, Domestic [Member] | Financing Receivables, 60 to 89 Days Past Due [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	846	658
Geographic Distribution, Domestic [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	1,840	1,421
Geographic Distribution, Foreign [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	8,115	7,903
Past due	317	283
Loans held for investment	8,432	8,186
Geographic Distribution, Foreign [Member] | Receivables Acquired with Deteriorated Credit Quality [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	0	0
Geographic Distribution, Foreign [Member] | Financing Receivables, 30 to 59 Days Past Due [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	124	110
Geographic Distribution, Foreign [Member] | Financing Receivables, 60 to 89 Days Past Due [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	72	67
Geographic Distribution, Foreign [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	$ 121	$ 106