Loans and Allowance for Credit Losses - Loans modified by class and modification type (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($)
Financing Receivable, Modifications [Line Items]
Loans modified during the period	$ 899
Financing Receivable, Percent Past Due	0.20%
Commercial Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	$ 182
Financing Receivable, Percent Past Due	0.10%
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	$ 40
Financing Receivable, Percent Past Due	0.10%
Residential Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	$ 152	[1]
Financing Receivable, Percent Past Due	0.10%	[1]
Credit Card Receivable [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	$ 94
Financing Receivable, Percent Past Due	0.40%
Other Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	$ 78
Financing Receivable, Percent Past Due	0.10%
Total Loans Excluding Loans Purchased Gnma Mortgage Pools [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	$ 546
Financing Receivable, Percent Past Due	0.10%
Loans Excluding Loans Purchased From Government National Mortgage Association Mortgage pools [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	$ 353	[1]
Financing Receivable, Percent Past Due	0.30%	[1]
Contractual Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	$ 210
Contractual Interest Rate Reduction [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	114
Contractual Interest Rate Reduction [Member] | Credit Card Receivable [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	94
Contractual Interest Rate Reduction [Member] | Other Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	2
Contractual Interest Rate Reduction [Member] | Total Loans Excluding Loans Purchased Gnma Mortgage Pools [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	210
Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	384
Payment Deferral [Member] | Residential Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	130	[1]
Payment Deferral [Member] | Other Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	11
Payment Deferral [Member] | Total Loans Excluding Loans Purchased Gnma Mortgage Pools [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	141
Payment Deferral [Member] | Loans Excluding Loans Purchased From Government National Mortgage Association Mortgage pools [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	243	[1]
Extended Maturity [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	216
Extended Maturity [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	68
Extended Maturity [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	12
Extended Maturity [Member] | Residential Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	10	[1]
Extended Maturity [Member] | Other Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	63
Extended Maturity [Member] | Total Loans Excluding Loans Purchased Gnma Mortgage Pools [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	153
Extended Maturity [Member] | Loans Excluding Loans Purchased From Government National Mortgage Association Mortgage pools [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	63	[1]
Multiple Modification [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	89
Multiple Modification [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	28
Multiple Modification [Member] | Residential Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	12	[1]
Multiple Modification [Member] | Other Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	2
Multiple Modification [Member] | Total Loans Excluding Loans Purchased Gnma Mortgage Pools [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	42
Multiple Modification [Member] | Loans Excluding Loans Purchased From Government National Mortgage Association Mortgage pools [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	$ 47	[1]

[1] Percent of class total amounts expressed as a percent of total residential mortgage loan balances.