Loans and Allowance for Loan Losses - FICO Scores (Details) - Consumer - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 42,894	$ 38,685
Percentage of total	100.00%	100.00%
720 and Above
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 34,938	$ 31,190
Percentage of total	82.00%	81.00%
Below 720
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 7,470	$ 7,000
Percentage of total	17.00%	18.00%
No FICO Available
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 486	$ 495
Percentage of total	1.00%	1.00%
Residential mortgage
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 38,045	$ 35,279
Residential mortgage | 720 and Above
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	31,589	28,786
Residential mortgage | Below 720
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	6,022	6,082
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	434	411
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	4,849	3,406
Home equity and other consumer loans | 720 and Above
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	3,349	2,404
Home equity and other consumer loans | Below 720
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	1,448	918
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	$ 52	$ 84