Loans and Allowance for Loan Losses - Loans in Consumer Portfolio Segment Based on Refreshed FICO Scores (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Consumer Loans
Credit quality of consumer loans
Percentage of total	100.00%
Consumer
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 42,048
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	34,008
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	7,583
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	457	[1]
Consumer | Other consumer
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	4,411
Consumer | Residential mortgage and home equity
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 37,637
FICO Score 720 and Above | Consumer Loans
Credit quality of consumer loans
Percentage of total	81.00%
FICO Score 720 and Above | Other consumer | Consumer Loans
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 2,567
FICO Score 720 and Above | Residential mortgage and home equity | Consumer Loans
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 31,441
FICO Score Below 720 | Consumer Loans
Credit quality of consumer loans
Percentage of total	18.00%
FICO Score Below 720 | Other consumer | Consumer Loans
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 1,841
FICO Score Below 720 | Residential mortgage and home equity | Consumer Loans
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 5,742
No FICO Available | Consumer Loans
Credit quality of consumer loans
Percentage of total	1.00%
No FICO Available | Other consumer | Consumer Loans
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 3
No FICO Available | Residential mortgage and home equity | Consumer Loans
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 454

[1] Represents loans for which management was not able to obtain an updated FICO score (e.g., due to recent profile changes).