Loans and Allowance for Loan Losses - Loans in Consumer Portfolio Segment Based on Refreshed LTV ratios (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Consumer Loans
Credit quality of consumer loans
Percentage of total loans categorized by LTV ratio	100.00%
Consumer
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 37,637
Consumer | Less than or Equal to 80 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	35,893
Consumer | Greater than 80 and Less than 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	1,689
Consumer | Greater than or Equal to 100 Percent
Credit quality of consumer loans
Loans categorized by LTV ratio	12
Consumer | No LTV Available
Credit quality of consumer loans
Loans categorized by LTV ratio	43	[1]
Consumer | Residential mortgage
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 37,637
Less than or Equal to 80 Percent | Consumer Loans
Credit quality of consumer loans
Percentage of total loans categorized by LTV ratio	95.00%
Less than or Equal to 80 Percent | residential mortgage and home equity [Member] | Consumer Loans
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 35,893
Greater than 80 and Less than 100 Percent | Consumer Loans
Credit quality of consumer loans
Percentage of total loans categorized by LTV ratio	5.00%
Greater than 80 and Less than 100 Percent | residential mortgage and home equity [Member] | Consumer Loans
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 1,689
Greater than or Equal to 100 Percent | Consumer Loans
Credit quality of consumer loans
Percentage of total loans categorized by LTV ratio	0.00%
Greater than or Equal to 100 Percent | residential mortgage and home equity [Member] | Consumer Loans
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 12
No LTV Available | Consumer Loans
Credit quality of consumer loans
Percentage of total loans categorized by LTV ratio	0.00%
No LTV Available | residential mortgage and home equity [Member] | Consumer Loans
Credit quality of consumer loans
Loans categorized by LTV ratio	$ 43

[1] Represents loans for which management was not able to obtain refreshed property values.