Loans and Allowance for Loan Losses - Pre and Post Modification Outstanding Recorded Investment Amounts of TDRs (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	$ 529	$ 173
Post-Modification Outstanding Recorded Investment	529	172
Commercial portfolio
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	504	134
Post-Modification Outstanding Recorded Investment	504	134
Commercial portfolio \| Commercial and industrial
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	495	111
Post-Modification Outstanding Recorded Investment	495	111
Commercial portfolio \| Commercial mortgage
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	9	23
Post-Modification Outstanding Recorded Investment	9	23
Consumer portfolio
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	25	39
Post-Modification Outstanding Recorded Investment	25	38
Consumer portfolio \| Residential mortgage
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	18	28
Post-Modification Outstanding Recorded Investment	18	27
Consumer portfolio \| Home equity and other consumer loans
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	7	11
Post-Modification Outstanding Recorded Investment	$ 7	$ 11

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Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953676-111524

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Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

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