Loans and Allowance for Loan Losses - Loans in Consumer Portfolio Segment Based on Refreshed FICO Scores (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Credit quality of consumer loans
Financing Receivable, Nonaccrual	$ 328	$ 421
Consumer
Credit quality of consumer loans
Percentage of total	100.00%	100.00%
Consumer | 720 and Above
Credit quality of consumer loans
Percentage of total	81.00%	82.00%
Consumer | Below 720
Credit quality of consumer loans
Percentage of total	18.00%	17.00%
Consumer | No FICO Available
Credit quality of consumer loans
Percentage of total	1.00%	1.00%
Consumer | Other Consumer Loans [Member]
Credit quality of consumer loans
Financing Receivable Recorded Investment Accrual Status	$ 4,449	$ 2,694
Financing Receivable, Nonaccrual	1	1
Consumer | Other Consumer Loans [Member] | 720 and Above
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	2,567	1,625
Consumer | Other Consumer Loans [Member] | Below 720
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	1,841	1,000
Consumer | Other Consumer Loans [Member] | No FICO Available
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	3	2
Consumer | residential mortgage and home equity [Member]
Credit quality of consumer loans
Financing Receivable Recorded Investment Accrual Status	37,878	40,532
Financing Receivable, Nonaccrual	137	139
Consumer | residential mortgage and home equity [Member] | 720 and Above
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	31,441	33,313
Consumer | residential mortgage and home equity [Member] | Below 720
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	5,742	6,470
Consumer | residential mortgage and home equity [Member] | No FICO Available
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	454	484
Consumer Portfolio Segment [Member]
Credit quality of consumer loans
Financing Receivable Recorded Investment Accrual Status	42,327	43,226
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	42,048	42,894
Financing Receivable, Nonaccrual	138	140
Loans and Leases Receivable Net of Deferred Income and Purchased Credit Impaired Loans	42,465	43,366
Consumer Portfolio Segment [Member] | residential mortgage and home equity [Member]
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	37,637	40,267
Loans and Leases Receivable Net of Deferred Income and Purchased Credit Impaired Loans	38,015	40,671
Consumer Portfolio Segment [Member] | Other Consumer Loans [Member]
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	4,411	2,627
Loans and Leases Receivable Net of Deferred Income and Purchased Credit Impaired Loans	4,450	2,695
No FICO Available | Consumer Portfolio Segment [Member]
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	457	486
Below 720 | Consumer Portfolio Segment [Member]
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	7,583	7,470
720 and Above | Consumer Portfolio Segment [Member]
Credit quality of consumer loans
Loan balances, excluding loans serviced by third parties and loans covered by FDIC loss share agreements	$ 34,008	$ 34,938