Loans and Related Allowance for Credit Losses (Financial Effect of Loan Modification) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 1,196	$ 566
Total commercial
Financing Receivable [Line Items]
Amortized cost basis, modified	1,118	497
Total commercial | Commercial and industrial
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 610	$ 224
Weighted-Average Interest Rate Reduction	4.06%
Weighted-Average Term Extension (in Months)	11 months	5 months
Weighted-Average Payment Delay (in Months)	5 months	2 months
Total commercial | Commercial and industrial | Total Principal Forgiveness
Financing Receivable [Line Items]
Amortized cost basis, modified		$ 2
Total commercial | Commercial real estate
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 508	$ 273
Weighted-Average Term Extension (in Months)	12 months	13 months
Weighted-Average Payment Delay (in Months)	8 months
Total consumer
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 78	$ 69
Total consumer | Residential real estate
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 43	$ 49
Weighted-Average Interest Rate Reduction		1.71%
Weighted-Average Term Extension (in Months)		145 months
Weighted-Average Payment Delay (in Months)	8 months	8 months
Total consumer | Home equity
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 11	$ 5
Weighted-Average Payment Delay (in Months)	4 months	6 months
Total consumer | Education
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 2	$ 1
Weighted-Average Term Extension (in Months)	10 months	12 months