Asset Quality - Schedule of Modifications for Borrowers Experiencing Financial Difficulty (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 431	$ 430
Amortized Cost Basis (as a percent)	0.41%	0.41%
Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 8	$ 32
Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	309	344
Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	25	15
Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	89	39
Total commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 398	$ 400
Amortized Cost Basis (as a percent)	0.53%	0.55%
Total commercial loans | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 2	$ 28
Total commercial loans | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	304	342
Total commercial loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	24	14
Total commercial loans | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	68	16
Total consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 33	$ 30
Amortized Cost Basis (as a percent)	0.11%	0.09%
Total consumer loans | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 6	$ 4
Total consumer loans | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	5	2
Total consumer loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	1	1
Total consumer loans | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	21	23
Commercial and Industrial | Total commercial real estate loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 116	$ 153
Amortized Cost Basis (as a percent)	0.20%	0.29%
Commercial and Industrial | Total commercial real estate loans | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 2	$ 0
Commercial and Industrial | Total commercial real estate loans | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	76	126
Commercial and Industrial | Total commercial real estate loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	22	11
Commercial and Industrial | Total commercial real estate loans | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	16	16
Total commercial real estate loans | Total commercial real estate loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 282	$ 247
Amortized Cost Basis (as a percent)	1.74%	1.48%
Total commercial real estate loans | Total commercial real estate loans | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 0	$ 28
Total commercial real estate loans | Total commercial real estate loans | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	228	216
Total commercial real estate loans | Total commercial real estate loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	2	3
Total commercial real estate loans | Total commercial real estate loans | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	52	0
Commercial mortgage | Total commercial real estate loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 248	$ 220
Amortized Cost Basis (as a percent)	1.85%	1.61%
Commercial mortgage | Total commercial real estate loans | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 0	$ 28
Commercial mortgage | Total commercial real estate loans | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	194	189
Commercial mortgage | Total commercial real estate loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	2	3
Commercial mortgage | Total commercial real estate loans | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	52	0
Construction | Total commercial real estate loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 34	$ 27
Amortized Cost Basis (as a percent)	1.21%	0.87%
Construction | Total commercial real estate loans | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 0	$ 0
Construction | Total commercial real estate loans | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	34	27
Construction | Total commercial real estate loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Construction | Total commercial real estate loans | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Real estate — residential mortgage | Total consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 13	$ 12
Amortized Cost Basis (as a percent)	0.07%	0.06%
Real estate — residential mortgage | Total consumer loans | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 2	$ 1
Real estate — residential mortgage | Total consumer loans | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	1	0
Real estate — residential mortgage | Total consumer loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Real estate — residential mortgage | Total consumer loans | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	10	11
Home equity loans | Total consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 11	$ 11
Amortized Cost Basis (as a percent)	0.19%	0.17%
Home equity loans | Total consumer loans | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 4	$ 3
Home equity loans | Total consumer loans | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	1	1
Home equity loans | Total consumer loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	1	1
Home equity loans | Total consumer loans | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	5	6
Other consumer loans | Total consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 6	$ 3
Amortized Cost Basis (as a percent)	0.13%	0.06%
Other consumer loans | Total consumer loans | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 0	$ 0
Other consumer loans | Total consumer loans | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	3	1
Other consumer loans | Total consumer loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Other consumer loans | Total consumer loans | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	3	2
Credit cards | Total consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 3	$ 4
Amortized Cost Basis (as a percent)	0.32%	0.44%
Credit cards | Total consumer loans | Interest Rate Reduction
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 0	$ 0
Credit cards | Total consumer loans | Term Extension
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Credit cards | Total consumer loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	0	0
Credit cards | Total consumer loans | Combination
Financing Receivable, Credit Quality Indicator [Line Items]
Amortized Cost Basis	$ 3	$ 4