Loans and Allowance for Loan Losses - FICO Scores (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Consumer
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 30,436	$ 31,958
Percentage of total	100.00%	100.00%
Consumer | FICO Score 720 and Above
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 23,545	$ 24,787
Percentage of total	77.00%	77.00%
Consumer | FICO Score Below 720
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 6,306	$ 6,582
Percentage of total	21.00%	21.00%
Consumer | No FICO Available
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 585	$ 589
Percentage of total	2.00%	2.00%
Consumer portfolio
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 30,288	$ 31,761
Consumer portfolio | FICO Score 720 and Above
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	23,485	24,714
Consumer portfolio | FICO Score Below 720
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	6,230	6,471
Consumer portfolio | No FICO Available
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	573	576
Consumer portfolio | Residential mortgage
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	27,109	28,715
Consumer portfolio | Residential mortgage | FICO Score 720 and Above
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	21,209	22,505
Consumer portfolio | Residential mortgage | FICO Score Below 720
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	5,412	5,717
Consumer portfolio | Residential mortgage | No FICO Available
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	488	493
Consumer portfolio | Home equity and other consumer loans
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	3,179	3,046
Consumer portfolio | Home equity and other consumer loans | FICO Score 720 and Above
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	2,276	2,209
Consumer portfolio | Home equity and other consumer loans | FICO Score Below 720
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	818	754
Consumer portfolio | Home equity and other consumer loans | No FICO Available
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	85	83
Purchased credit-impaired loans | Consumer
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	148	197
Purchased credit-impaired loans | Consumer | FICO Score 720 and Above
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	60	73
Purchased credit-impaired loans | Consumer | FICO Score Below 720
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	76	111
Purchased credit-impaired loans | Consumer | No FICO Available
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 12	$ 13