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, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	$ 476	$ 639	$ 723
(Reversal of) provision for loan losses	84	(65)	158
Other		2	2
Loans charged-off	(120)	(155)	(271)
Recoveries of loans previously charged-off	34	55	27
Allowance for loan losses, end of period	474	476	639
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	360	556	654
(Reversal of) provision for loan losses		(132)	134
Loans charged-off	(79)	(116)	(259)
Recoveries of loans previously charged-off	27	50	25
Allowance for loan losses, end of period	359	360	556
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	86	83	49
(Reversal of) provision for loan losses		37	44
Other		0	0
Loans charged-off	(41)	(39)	(12)
Recoveries of loans previously charged-off	7	5	2
Allowance for loan losses, end of period	110	86	83
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	30	0	20
(Reversal of) provision for loan losses		30	(20)
Other		0	0
Loans charged-off		0	0
Recoveries of loans previously charged-off		0	0
Allowance for loan losses, end of period	$ 5	$ 30	$ 0

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

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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.

+ Details

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- Definition

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

+ References

+ Details

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- Definition

Amount of direct write-downs of financing receivables charged against the allowance.

+ References

+ Details

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544

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Balance Type:	credit
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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.11)
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-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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