Loans and Allowance for Loan Losses - Average Recorded Investment in Impaired Loans (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loan impairment
Average Recorded Investment	$ 837	$ 595	$ 563
Recognized Interest Income	15	18	19
Allowance for loan losses:
Transfer of loans from held for investment to held for sale	1,976	1,207	203
Loans receivable sold during the period	1,526	1,338	292
Commercial
Loan impairment
Average Recorded Investment	547	269	224
Recognized Interest Income	5	7	7
Allowance for loan losses:
Transfer of loans from held for investment to held for sale	1,632	397	203
Loans receivable sold during the period	1,182	511	292
Commercial \| Commercial and industrial
Loan impairment
Average Recorded Investment	530	241	188
Recognized Interest Income	4	6	5
Commercial \| Commercial mortgage
Loan impairment
Average Recorded Investment	17	28	36
Recognized Interest Income	1	1	2
Commercial \| Construction
Loan impairment
Average Recorded Investment	0	0	0
Recognized Interest Income	0	0	0
Consumer
Loan impairment
Average Recorded Investment	289	324	337
Recognized Interest Income	10	11	12
Allowance for loan losses:
Transfer of loans from held for investment to held for sale	344	810	0
Loans receivable sold during the period	344	827	0
Consumer \| Residential mortgage
Loan impairment
Average Recorded Investment	258	294	310
Recognized Interest Income	8	9	10
Consumer \| Home equity and other consumer loans
Loan impairment
Average Recorded Investment	31	30	27
Recognized Interest Income	2	2	2
Total, excluding purchased credit-impaired loans
Loan impairment
Average Recorded Investment	836	593	561
Recognized Interest Income	15	18	19
Purchased Credit- Impaired
Loan impairment
Average Recorded Investment	1	2	2
Recognized Interest Income	$ 0	$ 0	$ 0

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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The amount of financing receivables reclassified to held for sale during the reporting period.

+ 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 (f)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524

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The amount of any significant sales of financing receivables during the reporting period.

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Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5258-111524

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Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

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