Loans - Loan Portfolio Composition and Aging Analysis (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	$ 203,030	$ 203,438
Past due	6,015	6,895
Loans held for investment	$ 227,613	$ 229,851	$ 203,978
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Financing Receivable, Percent Current	89.20%	88.51%
Total Delinquent Loans (as percent)	2.64%	3.00%
Total Loans (as percent)	100.00%	100.00%
Loans and Leases Receivable, Deferred Income	$ 948	$ 989
Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	89,778	92,857
Past due	2,921	3,268
Loans held for investment	92,699	96,125
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	50,366	48,528
Past due	2,590	3,284
Loans held for investment	70,591	70,372
Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	40,386	38,549
Past due	2,328	3,000
Loans held for investment	42,714	41,549
Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	6,521	6,465
Past due	218	235
Loans held for investment	24,343	25,227
Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	3,459	3,514
Past due	44	49
Loans held for investment	3,534	3,596
Commercial Banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	62,813	61,976
Past due	495	332
Loans held for investment	64,241	63,266
Commercial Banking | Total commercial lending
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	62,241	61,369
Past due	487	326
Loans held for investment	63,661	62,653
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	25,497	25,449
Past due	30	38
Loans held for investment	25,559	25,518
Commercial Banking | Commercial and industrial
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	36,744	35,920
Past due	457	288
Loans held for investment	38,102	37,135
Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	572	607
Past due	8	6
Loans held for investment	580	613
Other
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	73	77
Past due	9	11
Loans held for investment	82	88
Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	$ 18,568	$ 19,518
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Total Loans (as percent)	8.16%	8.49%
Receivables Acquired with Deteriorated Credit Quality [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	$ 0	$ 0
Receivables Acquired with Deteriorated Credit Quality [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	17,635	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	17,604	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	31	33
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial Banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	933	958
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial Banking | Total commercial lending
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	933	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	32	31
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial Banking | Commercial and industrial
Financing Receivable, Recorded Investment, Aging [Abstract]
Loans held for investment	901	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	$ 2,581	$ 3,069
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Total Delinquent Loans (as percent)	1.13%	1.33%
Financing Receivables, 30 to 59 Days Past Due [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	$ 873	$ 1,016
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	1,632	1,963
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	1,576	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	37	41
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	19	21
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	74	88
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Banking | Total commercial lending
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	71	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	19	34
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Banking | Commercial and industrial
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	52	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	3	3
Financing Receivables, 30 to 59 Days Past Due [Member] | Other
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	2	2
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	$ 1,371	$ 1,668
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Total Delinquent Loans (as percent)	0.60%	0.73%
Financing Receivables, 60 to 89 Days Past Due [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	$ 627	$ 725
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	641	906
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	619	880
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	15	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	102	35
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Banking | Total commercial lending
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	100	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	2	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Banking | Commercial and industrial
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	98	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	2	1
Financing Receivables, 60 to 89 Days Past Due [Member] | Other
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	1	2
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	$ 2,063	$ 2,158
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Total Delinquent Loans (as percent)	0.91%	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	$ 1,421	$ 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	317	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	133	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	166	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	18	20
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	319	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	316	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	9	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	307	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	3	2
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Other
Financing Receivable, Recorded Investment, Aging [Abstract]
Past due	6	7
Geographic Distribution, Domestic [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	81,946	84,954
Past due	2,615	2,985
Loans held for investment	84,561	87,939
Geographic Distribution, Domestic [Member] | Credit Card Portfolio Segment [Member] | Installment loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Gross	13	16
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	0	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	757	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	555	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	1,303	1,421
Geographic Distribution, Foreign [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	7,832	7,903
Past due	306	283
Loans held for investment	8,138	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	116	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	$ 118	$ 106