Loans and Allowance for Loan Losses - Loans in Consumer Portfolio Segment Based on Refreshed FICO Scores (Details) - USD ($) $ in Millions		6 Months Ended		12 Months Ended
		Jun. 30, 2018		Dec. 31, 2017
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		$ 40,960		$ 38,685
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		33,459		31,190
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		7,049		7,000
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]	452		495
Consumer | Residential mortgage
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements		37,167		35,279
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		$ 3,793		$ 3,406
FICO Score 720 and Above | Consumer Loans
Credit quality of consumer loans
Percentage of total		82.00%		81.00%
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		$ 30,742		$ 28,786
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		$ 2,717		$ 2,404
FICO Score Below 720 | Consumer Loans
Credit quality of consumer loans
Percentage of total		17.00%		18.00%
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		$ 6,028		$ 6,082
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		$ 1,021		$ 918
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		$ 397		$ 411
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		$ 55		$ 84

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