Allowance for Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	$ 963	$ 307
Charge-offs	(23)	(14)
Recoveries	15	6
Provision for credit losses	(45)	154
Ending Balance	914	444
Loans and leases	58,600		$ 58,232
Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	(41)	145
Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	85	30
Provision for credit losses	(4)	9
Ending Balance	81	39
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Loans and leases	33,951		33,104
Commercial \| Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	453	142
Charge-offs	(16)	(7)
Recoveries	6	1
Ending Balance	442	255
Loans and leases	33,951		33,104
Commercial \| Commercial and industrial \| Paycheck Protection Plan
Allowance for Loan and Lease Losses [Roll Forward]
Loans and leases	5,100		4,100
Commercial \| Commercial and industrial \| Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	(1)	119
Commercial \| Commercial and industrial \| Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	65	21
Provision for credit losses	(3)	6
Ending Balance	62	27
Commercial \| Commercial Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	242	29
Charge-offs	(3)	(1)
Recoveries	2	1
Ending Balance	232	48
Loans and leases	12,470		12,275
Commercial \| Commercial Real Estate \| Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	(8)	19
Commercial \| Commercial Real Estate \| Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	10	3
Provision for credit losses	1	3
Ending Balance	11	6
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Loans and leases	11,053		11,725
Consumer \| Consumer Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	242	121
Charge-offs	(1)	(2)
Recoveries	6	3
Ending Balance	222	122
Loans and leases	11,053		11,725
Consumer \| Consumer Real Estate \| Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	(25)	0
Consumer \| Consumer Real Estate \| Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	10	6
Provision for credit losses	(2)	0
Ending Balance	8	6
Consumer \| Credit Card and Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	26	15
Charge-offs	(3)	(4)
Recoveries	1	1
Ending Balance	18	19
Loans and leases	1,126		$ 1,128
Consumer \| Credit Card and Other \| Funded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	(6)	7
Consumer \| Credit Card and Other \| Unfunded commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	0	0
Provision for credit losses	0	0
Ending Balance	$ 0	$ 0

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amount of increase in allowance for credit loss on financing receivable from recovery.

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Amount of writeoff of financing receivable, charged against allowance for credit loss.

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Amount, before allowance for credit loss, of financing receivable.

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Amount of credit loss expense (reversal of expense) for financing receivable.

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