Loans, Leases, and Allowance for Credit Losses (Narrative) (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022	Apr. 30, 2023
Financing Receivable, Allowance for Credit Losses [Line Items]
Net unamortized purchase premiums, discounts, and deferred loan fees and cost	$ 43,000,000		$ 49,000,000
Accrued interest receivable	$ 254,000,000		$ 247,000,000
Financing Receivable, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Other assets		Other assets
Total loans	$ 56,331,000,000		$ 55,653,000,000
Loans held for sale	5,000,000		8,000,000
Held-for-sale loans sold	89,000,000	$ 336,000,000
Payments for origination and purchases of loans held-for-sale	86,000,000	297,000,000
Principal balance of loans sold, serviced loans	3,400,000,000		3,500,000,000
Total income from loans sold	5,000,000	6,000,000
Loans and leases, net of unearned income and fees	56,331,000,000		55,653,000,000
Financing receivable, commitments threshold for evaluating collectively or individually	1,000,000
Total allowance for credit losses	678,000,000	514,000,000
Unfunded lending commitments on troubled debt restructuring	8,000,000		7,000,000
Amortized cost of TDR loans modified with interest rates below market			235,000,000
Financing receivable, modifications, subsequent default, recorded investment			10,000,000
Real estate acquired through foreclosure	0		0
Mortgage loans in process of foreclosure	5,000,000		10,000,000
Interest income	0	0
Asset Pledged as Collateral without Right
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans held for sale	30,200,000,000		27,600,000,000
Asset Pledged as Collateral without Right | Subsequent Event
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans held for sale				$ 9,400,000,000
Nonaccruing
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost of TDR loans modified with interest rates below market			38,000,000
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	30,576,000,000		30,495,000,000
Total allowance for credit losses	332,000,000	296,000,000
Commercial | Nonaccruing
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost of TDR loans modified with interest rates below market			23,000,000
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	12,898,000,000		12,739,000,000
Total allowance for credit losses	188,000,000	114,000,000
Commercial real estate | Nonaccruing
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost of TDR loans modified with interest rates below market			10,000,000
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	12,857,000,000		12,419,000,000
Total allowance for credit losses	158,000,000	$ 104,000,000
Consumer | Nonaccruing
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost of TDR loans modified with interest rates below market			5,000,000
Land Acquisition and Development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	226,000,000		262,000,000
Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 16,500,000,000		16,377,000,000
Commercial and industrial | Commercial | Nonaccruing
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost of TDR loans modified with interest rates below market			$ 15,000,000