Loans and Allowance for Loan Losses (Details 4) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Nonaccrual loans
Nonaccrual loans, before purchased credit-impaired loans	$ 627	$ 546
Nonaccrual loans	632	552
Troubled debt restructured loans that continue to accrue interest	245	413
Troubled debt restructured nonaccrual loans (included in the total nonaccrual loans above)	390	409
Commercial portfolio
Nonaccrual loans
Nonaccrual loans	422	321
Commercial portfolio | Commercial and industrial
Nonaccrual loans
Nonaccrual loans	396	284
Commercial portfolio | Commercial mortgage
Nonaccrual loans
Nonaccrual loans	26	37
Consumer portfolio
Nonaccrual loans
Nonaccrual loans	205	225
Consumer portfolio | Residential mortgage
Nonaccrual loans
Nonaccrual loans	177	190
Consumer portfolio | Home equity and other consumer loans
Nonaccrual loans
Nonaccrual loans	28	35
Purchased credit-impaired loans
Nonaccrual loans
Nonaccrual loans	$ 5	$ 6