Loan Portfolio (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 105,902	$ 104,260
Accrued interest	472	456
Discontinued operations | Education Lending
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	216	257
Total commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	75,319	71,891
Accrued interest	351	322
Total commercial loans | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	56,791	52,909
Total commercial loans | Commercial and industrial | Collateral Pledged
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		211
Total commercial loans | Total commercial real estate loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	16,195	16,246
Total commercial loans | Commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	13,378	13,310
Total commercial loans | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,817	2,936
Total commercial loans | Commercial lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,333	2,736
Total commercial loans | Commercial lease financing | Collateral Pledged
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1	3
Total commercial loans | Credit cards
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	212	212
Total consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	30,583	32,369
Accrued interest	121	134
Total consumer loans | Real estate — residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	19,008	19,886
Total consumer loans | Home equity loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	5,863	6,358
Total consumer loans | Total residential loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	24,871	26,244
Total consumer loans | Other consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	4,779	5,167
Total consumer loans | Credit cards
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 933	$ 958