Allowance for Loan and Lease Losses - Components of Allowance for Loan and Lease Losses by Impairment Methodology (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	$ 4,924	$ 4,744
Asset-specific	457	349
Total allowance for loan and lease losses	5,416	5,130
Loans held for investment by impairment methodology:
Collectively evaluated	206,324	208,084
Asset-specific	2,721	2,249
Loans held for investment	$ 227,613	$ 229,851	$ 203,978
Allowance as a percentage of period-end loans held for investment	2.38%	2.23%
Credit Card Portfolio Segment [Member]
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	$ 3,572	$ 3,445
Asset-specific	213	209
Total allowance for loan and lease losses	3,785	3,654	3,130	$ 3,204
Loans held for investment by impairment methodology:
Collectively evaluated	92,041	95,459
Asset-specific	658	666
Loans held for investment	$ 92,699	$ 96,125
Allowance as a percentage of period-end loans held for investment	4.08%	3.80%
Consumer Portfolio Segment [Member]
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	$ 829	$ 778
Asset-specific	51	54
Total allowance for loan and lease losses	914	868	826	779
Loans held for investment by impairment methodology:
Collectively evaluated	52,247	51,113
Asset-specific	709	699
Loans held for investment	$ 70,591	$ 70,372
Allowance as a percentage of period-end loans held for investment	1.29%	1.23%
Commercial Banking
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	$ 520	$ 517
Asset-specific	193	86
Total allowance for loan and lease losses	714	604	444	395
Loans held for investment by impairment methodology:
Collectively evaluated	61,954	61,424
Asset-specific	1,354	884
Loans held for investment	$ 64,241	$ 63,266
Allowance as a percentage of period-end loans held for investment	1.11%	0.95%
Other
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	$ 3	$ 4
Asset-specific	0	0
Total allowance for loan and lease losses	3	4	$ 5	$ 5
Loans held for investment by impairment methodology:
Collectively evaluated	82	88
Asset-specific	0	0
Loans held for investment	$ 82	$ 88
Allowance as a percentage of period-end loans held for investment	4.15%	4.94%
Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loan and lease losses by impairment methodology:
Financing Receivable, Allowance for Credit Losses	$ 35	$ 37
Loans held for investment by impairment methodology:
Loans held for investment	18,568	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	0	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	34	36
Loans held for investment by impairment methodology:
Loans held for investment	17,635	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	1	1
Loans held for investment by impairment methodology:
Loans held for investment	933	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