Asset Quality - Schedule of Modifications for Borrowers Experiencing Financial Difficulty (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 247	$ 190
Amortized Cost Basis (as a percent)	0.23%	0.16%
Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 32	$ 1
Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	115	152
Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	45	21
Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	55	16
Total commercial real estate loans | Commercial and Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 146	$ 168
Amortized Cost Basis (as a percent)	0.27%	0.28%
Total commercial real estate loans | Commercial and Industrial | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 0	$ 0
Total commercial real estate loans | Commercial and Industrial | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	73	144
Total commercial real estate loans | Commercial and Industrial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	40	19
Total commercial real estate loans | Commercial and Industrial | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	33	5
Total commercial real estate loans | Total commercial real estate loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 72	$ 7
Amortized Cost Basis (as a percent)	0.42%	0.04%
Total commercial real estate loans | Total commercial real estate loans | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 28	$ 0
Total commercial real estate loans | Total commercial real estate loans | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	40	7
Total commercial real estate loans | Total commercial real estate loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	4	0
Total commercial real estate loans | Total commercial real estate loans | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Total commercial real estate loans | Commercial mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 42	$ 7
Amortized Cost Basis (as a percent)	0.30%	0.04%
Total commercial real estate loans | Commercial mortgage | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 28	$ 0
Total commercial real estate loans | Commercial mortgage | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	10	7
Total commercial real estate loans | Commercial mortgage | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	4	0
Total commercial real estate loans | Commercial mortgage | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Total commercial real estate loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 30	$ 0
Amortized Cost Basis (as a percent)	0.97%	0.00%
Total commercial real estate loans | Construction | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 0	$ 0
Total commercial real estate loans | Construction | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	30	0
Total commercial real estate loans | Construction | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Total commercial real estate loans | Construction | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Total commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 218	$ 175
Amortized Cost Basis (as a percent)	0.30%	0.21%
Total commercial loans | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 28	$ 0
Total commercial loans | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	113	151
Total commercial loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	44	19
Total commercial loans | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	33	5
Total commercial loans | Commercial lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 0	$ 0
Amortized Cost Basis (as a percent)	0.00%	0.00%
Total commercial loans | Commercial lease financing | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 0	$ 0
Total commercial loans | Commercial lease financing | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Total commercial loans | Commercial lease financing | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Total commercial loans | Commercial lease financing | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Total consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 29	$ 15
Amortized Cost Basis (as a percent)	0.09%	0.04%
Total consumer loans | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 4	$ 1
Total consumer loans | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	2	1
Total consumer loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	1	2
Total consumer loans | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	22	11
Total consumer loans | Real estate — residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 10	$ 6
Amortized Cost Basis (as a percent)	0.05%	0.03%
Total consumer loans | Real estate — residential mortgage | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 1	$ 0
Total consumer loans | Real estate — residential mortgage | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Total consumer loans | Real estate — residential mortgage | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	1
Total consumer loans | Real estate — residential mortgage | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	9	5
Total consumer loans | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 11	$ 5
Amortized Cost Basis (as a percent)	0.16%	0.07%
Total consumer loans | Home equity loans | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 3	$ 1
Total consumer loans | Home equity loans | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	1	0
Total consumer loans | Home equity loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	1	1
Total consumer loans | Home equity loans | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	6	3
Total consumer loans | Other consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 4	$ 2
Amortized Cost Basis (as a percent)	0.07%	0.03%
Total consumer loans | Other consumer loans | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 0	$ 0
Total consumer loans | Other consumer loans | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	1	1
Total consumer loans | Other consumer loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Total consumer loans | Other consumer loans | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	3	1
Total consumer loans | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 4	$ 2
Amortized Cost Basis (as a percent)	0.43%	0.20%
Total consumer loans | Credit cards | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 0	$ 0
Total consumer loans | Credit cards | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Total consumer loans | Credit cards | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Total consumer loans | Credit cards | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 4	$ 2