Loans and Allowance for Loan Losses (Details 10) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Pre- and Post - modification recorded investments
Commitment to lend additional funds to borrowers with loan modifications classified as TDRs		$ 23	$ 33
Total excluding purchased credit-impaired loans	[1]	466	466
Commercial portfolio
Pre- and Post - modification recorded investments
Total excluding purchased credit-impaired loans		149	128
Commercial portfolio | Commercial and industrial
Pre- and Post - modification recorded investments
Total excluding purchased credit-impaired loans		129	100
Commercial portfolio | Commercial mortgage
Pre- and Post - modification recorded investments
Total excluding purchased credit-impaired loans		20	28
Consumer portfolio
Pre- and Post - modification recorded investments
Total excluding purchased credit-impaired loans		317	338
Consumer portfolio | Residential mortgage
Pre- and Post - modification recorded investments
Total excluding purchased credit-impaired loans		289	308
Consumer portfolio | Home equity and other consumer loans
Pre- and Post - modification recorded investments
Total excluding purchased credit-impaired loans		$ 28	$ 30

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