Loans and Allowance for Loan Losses - Reconciliation of Changes in Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	$ 474	$ 476	$ 639
(Reversal of) provision for loan losses	283	84	(65)
Other			2
Loans charged-off	(256)	(120)	(155)
Recoveries of loans previously charged-off	37	34	55
Allowance for loan losses, end of period	538	474	476
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Loans charged-off	(158)	(79)	(116)
Recoveries of loans previously charged-off	29	27	50
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Loans charged-off	(98)	(41)	(39)
Recoveries of loans previously charged-off	8	7	5
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	5
Allowance for loan losses, end of period	0	5
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	110	86
(Reversal of) provision for loan losses	164	58	37
Other			0
Allowance for loan losses, end of period	184	110	86
Consumer Portfolio Segment [Member] \| Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	110	86	83
Allowance for loan losses, end of period		110	86
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	5	30
(Reversal of) provision for loan losses	(5)	(25)	30
Other			0
Loans charged-off	0	0	0
Recoveries of loans previously charged-off	0	0	0
Allowance for loan losses, end of period	0	5	30
Unallocated \| Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	5	30	0
Allowance for loan losses, end of period		5	30
Commercial Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	359	360
(Reversal of) provision for loan losses	124	51	(132)
Other			2
Allowance for loan losses, end of period	354	359	360
Commercial Portfolio Segment [Member] \| Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	$ 359	360	556
Allowance for loan losses, end of period		$ 359	$ 360

Represents the amount of other allowance for credit losses related to financing receivable.

No definition available.

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- Definition

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

+ References

No definition available.

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- Definition

Amount of recovery of financing receivables doubtful of collection that were previously charged off.

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- Definition

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

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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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