Loans and Allowance for Loan Losses (Details 11) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	[1]	$ 8	$ 39	$ 134	$ 151
Post-Modification Outstanding Recorded Investment	[2]	8	39	134	150
Commercial portfolio
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	[1]	4	27	118	125
Post-Modification Outstanding Recorded Investment	[2]	4	27	118	125
Commercial portfolio | Commercial and industrial
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	[1]	4	25	110	105
Post-Modification Outstanding Recorded Investment	[2]	4	25	110	105
Commercial portfolio | Commercial mortgage
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	[1]	0	2	8	20
Post-Modification Outstanding Recorded Investment	[2]	0	2	8	20
Consumer portfolio
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	[1]	4	12	16	26
Post-Modification Outstanding Recorded Investment	[2]	4	12	16	25
Consumer portfolio | Residential mortgage
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	[1]	3	7	13	17
Post-Modification Outstanding Recorded Investment	[2]	3	7	13	16
Consumer portfolio | Home equity and other consumer loans
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	[1]	1	5	3	9
Post-Modification Outstanding Recorded Investment	[2]	$ 1	$ 5	$ 3	$ 9

[1] Represents the recorded investment in the loan immediately prior to the restructuring event.

[2] Represents the recorded investment in the loan immediately following the restructuring event. It includes the effect of paydowns that were required as part of the restructuring terms.