Allowance for Credit Losses - Rollforward of Allowance for Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Allowance for loan and lease losses:
Beginning balance	$ 738	$ 815
Charge-offs	(45)	(41)
Recoveries	17	12
Provision for loan and lease losses	20	36
Ending balance	730	822
Reserve for remaining unfunded commitments:
Beginning balance	101	79
Provision for remaining unfunded commitments	(5)	4
Ending balance	96	83
Allowance for credit losses	826	905
Commercial | Commercial, Financial, and Industrial
Allowance for loan and lease losses:
Beginning balance	335	345
Charge-offs	(36)	(34)
Recoveries	14	6
Provision for loan and lease losses	40	28
Ending balance	353	345
Reserve for remaining unfunded commitments:
Beginning balance	81	57
Provision for remaining unfunded commitments	(1)	6
Ending balance	80	63
Allowance for credit losses	433	408
Commercial | Commercial Real Estate
Allowance for loan and lease losses:
Beginning balance	177	227
Charge-offs	(4)	(3)
Recoveries	0	4
Provision for loan and lease losses	(17)	(3)
Ending balance	156	225
Reserve for remaining unfunded commitments:
Beginning balance	11	11
Provision for remaining unfunded commitments	(4)	(2)
Ending balance	7	9
Allowance for credit losses	163	234
Consumer | Consumer Real Estate
Allowance for loan and lease losses:
Beginning balance	206	221
Charge-offs	(1)	0
Recoveries	2	1
Provision for loan and lease losses	(6)	8
Ending balance	201	230
Reserve for remaining unfunded commitments:
Beginning balance	9	11
Provision for remaining unfunded commitments	0	0
Ending balance	9	11
Allowance for credit losses	210	241
Consumer | Credit Card and Other
Allowance for loan and lease losses:
Beginning balance	20	22
Charge-offs	(4)	(4)
Recoveries	1	1
Provision for loan and lease losses	3	3
Ending balance	20	22
Reserve for remaining unfunded commitments:
Beginning balance	0	0
Provision for remaining unfunded commitments	0	0
Ending balance	0	0
Allowance for credit losses	$ 20	$ 22