Loans and Allowance for Credit Losses - Summary of Financing Receivable credit losses charged-off by portfolio class (Detail) $ in Millions	Mar. 31, 2023 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Originated in 2023
Originated in 2022	104
Originated in 2021	15
Originated in 2020	10
Originated in 2019	16
Originated prior to 2019	54
Revolving	270
Total charge-offs	469
Credit Card Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Originated in 2023
Revolving	215
Total charge-offs	215
Residential Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Originated in 2023
Originated in 2019	1
Originated prior to 2019	3
Total charge-offs	4
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Originated in 2023
Originated in 2022	88	[1]
Originated in 2019	3	[1]
Originated prior to 2019	32	[1]
Total charge-offs	123	[1]
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Originated in 2023
Originated in 2022	6
Originated in 2021	4
Originated in 2020	4
Originated in 2019	5
Originated prior to 2019	11
Revolving	33
Total charge-offs	63
Other Retail Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Originated in 2023
Originated in 2022	10
Originated in 2021	11
Originated in 2020	6
Originated in 2019	7
Originated prior to 2019	8
Revolving	22
Total charge-offs	$ 64

[1] Primarily related to uncollectible amounts on acquired loans.