Loans and Allowance for Loan Losses - Loans in Consumer Portfolio Segment Based on Refreshed FICO Scores (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2019		Dec. 31, 2018
Consumer Loans
Credit quality of consumer loans
Percentage of total		100.00%		100.00%
Consumer
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements		$ 43,522		$ 42,894
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		35,404		34,938
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		7,662		7,470
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	[1]	456		486
Consumer | Residential mortgage
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements		38,046		38,045
Consumer | 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		$ 5,476		$ 4,849
FICO Score 720 and Above | Consumer Loans
Credit quality of consumer loans
Percentage of total		81.00%		82.00%
FICO Score 720 and Above | Residential mortgage | Consumer Loans
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements		$ 31,693		$ 31,589
FICO Score 720 and Above | Home equity and other consumer loans | Consumer Loans
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements		$ 3,711		$ 3,349
FICO Score Below 720 | Consumer Loans
Credit quality of consumer loans
Percentage of total		18.00%		17.00%
FICO Score Below 720 | Residential mortgage | Consumer Loans
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements		$ 5,950		$ 6,022
FICO Score Below 720 | Home equity and other consumer loans | Consumer Loans
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements		$ 1,712		$ 1,448
No FICO Available | Consumer Loans
Credit quality of consumer loans
Percentage of total		1.00%	[1]	1.00%
No FICO Available | Residential mortgage | Consumer Loans
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements		$ 403		$ 434
No FICO Available | Home equity and other consumer loans | Consumer Loans
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements		$ 53		$ 52

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