Loans, Leases, and Allowance for Credit Losses (Summary of Changes in the Allowance for Credit Losses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Allowance for loan losses
Balance at beginning of period	$ 699	$ 618	$ 684	$ 575	$ 575
Provision for loan losses	12	46	33	92
Total	21	22	35	29	62
Recoveries	6	9	14	16
Net loan and lease charge-offs (recoveries)	15	13	21	13
Balance at end of period	696	651	696	651	684
Reserve for unfunded lending commitments
Balance at beginning of period	37	60	45	61	61
Provision for unfunded lending commitments	(7)	0	(15)	(1)
Balance at end of period	30	60	30	60	45
Total allowance for credit losses	726	711	726	711
Adjustment for change in accounting standard
Allowance for loan losses
Balance at beginning of period				(3)	(3)
Adjusted balance
Allowance for loan losses
Balance at beginning of period				572	572
Commercial
Allowance for loan losses
Balance at beginning of period	296	313	302	300	300
Provision for loan losses	10	24	8	34
Total	8	20	18	23	45
Recoveries	4	6	10	12
Net loan and lease charge-offs (recoveries)	4	14	8	11
Balance at end of period	302	323	302	323	302
Reserve for unfunded lending commitments
Balance at beginning of period	19	19	19	16	16
Provision for unfunded lending commitments	(3)	1	(3)	4
Balance at end of period	16	20	16	20	19
Total allowance for credit losses	318	343	318	343
Commercial | Adjustment for change in accounting standard
Allowance for loan losses
Balance at beginning of period				0	0
Commercial | Adjusted balance
Allowance for loan losses
Balance at beginning of period				300	300
Commercial real estate
Allowance for loan losses
Balance at beginning of period	299	160	241	156	156
Provision for loan losses	12	21	69	29
Total	11	0	11	0	3
Recoveries	0	0	1	0
Net loan and lease charge-offs (recoveries)	11	0	10	0
Balance at end of period	300	181	300	181	241
Reserve for unfunded lending commitments
Balance at beginning of period	10	28	17	33	33
Provision for unfunded lending commitments	(3)	1	(10)	(4)
Balance at end of period	7	29	7	29	17
Total allowance for credit losses	307	210	307	210
Commercial real estate | Adjustment for change in accounting standard
Allowance for loan losses
Balance at beginning of period				(4)	(4)
Commercial real estate | Adjusted balance
Allowance for loan losses
Balance at beginning of period				152	152
Consumer
Allowance for loan losses
Balance at beginning of period	104	145	141	119	119
Provision for loan losses	(10)	1	(44)	29
Total	2	2	6	6	14
Recoveries	2	3	3	4
Net loan and lease charge-offs (recoveries)	0	(1)	3	2
Balance at end of period	94	147	94	147	141
Reserve for unfunded lending commitments
Balance at beginning of period	8	13	9	12	12
Provision for unfunded lending commitments	(1)	(2)	(2)	(1)
Balance at end of period	7	11	7	11	9
Total allowance for credit losses	$ 101	$ 158	$ 101	158
Consumer | Adjustment for change in accounting standard
Allowance for loan losses
Balance at beginning of period				1	1
Consumer | Adjusted balance
Allowance for loan losses
Balance at beginning of period				$ 120	$ 120