Loans and Allowance for Credit Losses - Summary Of Loans That Defaulted And Modified (Detail) - USD ($) $ in Millions		3 Months Ended	6 Months Ended
		Jun. 30, 2023	Jun. 30, 2023
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		$ 1,123	$ 1,879
Contractual Interest Rate Reduction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		106	337
Payment Deferral [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		546	869
Extended Maturity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		368	511
Multiple Modification [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period	[1]	103	162
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Contractual Interest Rate Reduction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		6	6
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Payment Deferral [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		9	9
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Extended Maturity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		2	2
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Multiple Modification [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		3	3
Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		149	318
Commercial Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		13	159
Commercial Portfolio Segment [Member] | Extended Maturity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		136	159
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Contractual Interest Rate Reduction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		1	1
Residential Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period	[2]	89	233
Residential Portfolio Segment [Member] | Payment Deferral [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period	[2]	79	202
Residential Portfolio Segment [Member] | Extended Maturity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period	[2]	6	15
Residential Portfolio Segment [Member] | Multiple Modification [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period	[1],[2]	4	16
Residential Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Payment Deferral [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		1	1
Residential Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Multiple Modification [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		1	1
Credit Card Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		91	174
Credit Card Receivable [Member] | Contractual Interest Rate Reduction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		91	174
Credit Card Receivable [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Contractual Interest Rate Reduction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		5	5
Other Retail Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		56	106
Other Retail Loans [Member] | Contractual Interest Rate Reduction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		2	4
Other Retail Loans [Member] | Payment Deferral [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		14	18
Other Retail Loans [Member] | Extended Maturity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		39	81
Other Retail Loans [Member] | Multiple Modification [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period	[1]	1	3
Other Retail Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Payment Deferral [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		2	2
Other Retail Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Extended Maturity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		1	1
Total Loans Excluding Loans Purchased Gnma Mortgage Pools [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		486	940
Total Loans Excluding Loans Purchased Gnma Mortgage Pools [Member] | Contractual Interest Rate Reduction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		106	337
Total Loans Excluding Loans Purchased Gnma Mortgage Pools [Member] | Payment Deferral [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		93	220
Total Loans Excluding Loans Purchased Gnma Mortgage Pools [Member] | Extended Maturity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		282	364
Total Loans Excluding Loans Purchased Gnma Mortgage Pools [Member] | Multiple Modification [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period	[1]	5	19
Total Loans Excluding Loans Purchased Gnma Mortgage Pools [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Contractual Interest Rate Reduction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		6	6
Total Loans Excluding Loans Purchased Gnma Mortgage Pools [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Payment Deferral [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		3	3
Total Loans Excluding Loans Purchased Gnma Mortgage Pools [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Extended Maturity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		1	1
Total Loans Excluding Loans Purchased Gnma Mortgage Pools [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Multiple Modification [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		1	1
Loans Excluding Loans Purchased From Government National Mortgage Association Mortgage pools [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Payment Deferral [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		6	6
Loans Excluding Loans Purchased From Government National Mortgage Association Mortgage pools [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Extended Maturity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		1	1
Loans Excluding Loans Purchased From Government National Mortgage Association Mortgage pools [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Multiple Modification [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans modified during the period		$ 2	$ 2

[1] Includes $100 million of total loans receiving a payment delay and term extension, $2 million of total loans receiving an interest rate reduction and term extension and $1 million of total loans receiving an interest rate reduction, payment delay and term extension for three months ended ended June 30, 2023. Includes $151 million of total loans receiving a payment delay and term extension, $5 million of total loans receiving an interest rate reduction and term extension and $6 million of total loans receiving an interest rate reduction, payment delay and term extension for six months ended ended June 30, 2023.

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