Loans, Leases, and Allowance for Credit Losses (Summary of Changes in the Allowance for Credit Losses) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Allowance for loan losses
Balance at beginning of period	$ 513	$ 777
Provision for loan and lease losses	(29)	(123)
Gross loan and lease charge-offs	17	21
Recoveries	11	13
Net loan and lease charge-offs (recoveries)	6	8
Balance at end of period	478	646
Reserve for unfunded lending commitments
Balance at beginning of period	40	58
Provision for unfunded lending commitments	(4)	(9)
Balance at end of period	36	49
Total allowance for credit losses	514	695
Commercial
Allowance for loan losses
Balance at beginning of period	311	464
Provision for loan and lease losses	(24)	(94)
Gross loan and lease charge-offs	13	18
Recoveries	8	10
Net loan and lease charge-offs (recoveries)	5	8
Balance at end of period	282	362
Reserve for unfunded lending commitments
Balance at beginning of period	19	30
Provision for unfunded lending commitments	(5)	(6)
Balance at end of period	14	24
Total allowance for credit losses	296	386
Commercial real estate
Allowance for loan losses
Balance at beginning of period	107	171
Provision for loan and lease losses	(5)	(19)
Gross loan and lease charge-offs	0	0
Recoveries	0	0
Net loan and lease charge-offs (recoveries)	0	0
Balance at end of period	102	152
Reserve for unfunded lending commitments
Balance at beginning of period	11	20
Provision for unfunded lending commitments	1	(3)
Balance at end of period	12	17
Total allowance for credit losses	114	169
Consumer
Allowance for loan losses
Balance at beginning of period	95	142
Provision for loan and lease losses	0	(10)
Gross loan and lease charge-offs	4	3
Recoveries	3	3
Net loan and lease charge-offs (recoveries)	1	0
Balance at end of period	94	132
Reserve for unfunded lending commitments
Balance at beginning of period	10	8
Provision for unfunded lending commitments	0	0
Balance at end of period	10	8
Total allowance for credit losses	$ 104	$ 140