Loans and Allowance for Loan Losses (Details 11) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	[1]	$ 133	$ 47	$ 193	$ 126
Post-Modification Outstanding Recorded Investment	[2]	132	47	192	126
Commercial portfolio
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	[1]	129	40	184	114
Post-Modification Outstanding Recorded Investment	[2]	128	40	183	114
Commercial portfolio | Commercial and industrial
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	[1]	126	34	176	106
Post-Modification Outstanding Recorded Investment	[2]	125	34	175	106
Commercial portfolio | Commercial mortgage
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	[1]	3	6	8	8
Post-Modification Outstanding Recorded Investment	[2]	3	6	8	8
Consumer portfolio
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	[1]	4	7	9	12
Post-Modification Outstanding Recorded Investment	[2]	4	7	9	12
Consumer portfolio | Residential mortgage
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	[1]	2	6	6	10
Post-Modification Outstanding Recorded Investment	[2]	2	6	6	10
Consumer portfolio | Home equity and other consumer loans
Pre- and Post - modification recorded investments
Pre-Modification Outstanding Recorded Investment	[1]	2	1	3	2
Post-Modification Outstanding Recorded Investment	[2]	$ 2	$ 1	$ 3	$ 2

[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.