Allowance for Loan and Lease Losses - Components of Allowance for Loan and Lease Losses by Impairment Methodology (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	$ 6,007	$ 4,744
Asset-specific	465	349
Total allowance for loan and lease losses	6,503	5,130
Loans held for investment by impairment methodology:
Collectively evaluated	227,555	208,084
Asset-specific	2,960	2,249
Loans held for investment	$ 245,586	$ 229,851	$ 208,316
Allowance as a percentage of period-end loans held for investment	2.65%	2.23%
Credit Card Portfolio Segment [Member]
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	$ 4,367	$ 3,445
Asset-specific	239	209
Total allowance for loan and lease losses	4,606	3,654	3,204	$ 3,214
Loans held for investment by impairment methodology:
Collectively evaluated	104,835	95,459
Asset-specific	715	666
Loans held for investment	$ 105,552	$ 96,125
Allowance as a percentage of period-end loans held for investment	4.36%	3.80%
Consumer Portfolio Segment [Member]
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	$ 1,016	$ 778
Asset-specific	57	54
Total allowance for loan and lease losses	1,102	868	779	752
Loans held for investment by impairment methodology:
Collectively evaluated	57,862	51,113
Asset-specific	736	699
Loans held for investment	$ 73,054	$ 70,372
Allowance as a percentage of period-end loans held for investment	1.51%	1.23%
Commercial Banking
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	$ 622	$ 517
Asset-specific	169	86
Total allowance for loan and lease losses	793	604	395	338
Loans held for investment by impairment methodology:
Collectively evaluated	64,794	61,424
Asset-specific	1,509	884
Loans held for investment	$ 66,916	$ 63,266
Allowance as a percentage of period-end loans held for investment	1.19%	0.95%
Other
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	$ 2	$ 4
Asset-specific	0	0
Total allowance for loan and lease losses	2	4	$ 5	$ 11
Loans held for investment by impairment methodology:
Collectively evaluated	64	88
Asset-specific	0	0
Loans held for investment	$ 64	$ 88
Allowance as a percentage of period-end loans held for investment	3.13%	4.94%
Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loan and lease losses by impairment methodology:
Financing Receivable, Allowance for Credit Losses	$ 31	$ 37
Loans held for investment by impairment methodology:
Loans held for investment	15,071	19,518
Receivables Acquired with Deteriorated Credit Quality [Member] | Credit Card Portfolio Segment [Member]
Allowance for loan and lease losses by impairment methodology:
Financing Receivable, Allowance for Credit Losses	0	0
Loans held for investment by impairment methodology:
Loans held for investment	2	0
Receivables Acquired with Deteriorated Credit Quality [Member] | Consumer Portfolio Segment [Member]
Allowance for loan and lease losses by impairment methodology:
Financing Receivable, Allowance for Credit Losses	29	36
Loans held for investment by impairment methodology:
Loans held for investment	14,456	18,560
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial Banking
Allowance for loan and lease losses by impairment methodology:
Financing Receivable, Allowance for Credit Losses	2	1
Loans held for investment by impairment methodology:
Loans held for investment	613	958
Receivables Acquired with Deteriorated Credit Quality [Member] | Other
Allowance for loan and lease losses by impairment methodology:
Financing Receivable, Allowance for Credit Losses	0	0
Loans held for investment by impairment methodology:
Loans held for investment	$ 0	$ 0