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, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	$ 537	$ 568	$ 653
(Reversal of) provision for loan losses	214	(16)	(53)
Other	(2)	(3)
Loans charged off	(48)	(50)	(77)
Recoveries of loans previously charged off	20	38	45
Allowance for loan losses, end of period	721	537	568
Commercial portfolio
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	465	421	418
(Reversal of) provision for loan losses	199	52	18
Loans charged off	(28)	(38)	(44)
Recoveries of loans previously charged off	17	33	29
Allowance for loan losses, end of period	651	465	421
Consumer portfolio
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	49	69	124
(Reversal of) provision for loan losses	6	(13)	(29)
Loans charged off	(8)	(11)	(30)
Recoveries of loans previously charged off	2	4	4
Allowance for loan losses, end of period	49	49	69
Purchased credit-impaired loans
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	3	1	1
(Reversal of) provision for loan losses	9	2	(9)
Loans charged off	(12)	(1)	(3)
Recoveries of loans previously charged off	1	1	12
Allowance for loan losses, end of period	1	3	1
Unallocated portfolio
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period	20	77	110
(Reversal of) provision for loan losses	0	(57)	(33)
Allowance for loan losses, end of period	$ 20	$ 20	$ 77

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.

+ 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=49124121&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524

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
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 6
-Section L
-Subsection 1

+ Details

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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)
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524

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