Loans - Consumer, Excluding Credit Card Loans, Impaired Loans (Details) - Consumer, excluding credit card $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) payment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Impaired loans
Loans modified subsequent to repurchase from Ginnie Mae	$ 4,100	$ 3,800
TDRs not having yet made six payments	2,000	2,200
Total residential real estate – excluding PCI
Impaired loans
With an allowance	4,523	5,643
Without an allowance	2,054	2,095
Total impaired loans	6,577	7,738
Allowance for loan losses related to impaired loans	133	173
Unpaid principal balance of impaired loans	9,673	11,442
Impaired loans on nonaccrual status	2,414	2,775
Average impaired loans	7,160	7,986	$ 8,687
Interest income on impaired loans	388	414	430
Interest income on impaired loans on a cash basis	$ 159	155	157
Number of payments under modified terms to recognize interest on cash basis | payment	6
Residential mortgage
Impaired loans
With an allowance	$ 3,381	4,407
Without an allowance	1,184	1,213
Total impaired loans	4,565	5,620
Allowance for loan losses related to impaired loans	88	62
Unpaid principal balance of impaired loans	6,207	7,741
Impaired loans on nonaccrual status	1,459	1,743
Average impaired loans	5,082	5,797	6,376
Interest income on impaired loans	257	287	305
Interest income on impaired loans on a cash basis	$ 75	75	77
Residential mortgage | Permanent Modification
Impaired loans
Rate of default for modified loans, estimated weighted-average	13.00%
Home equity
Impaired loans
With an allowance	$ 1,142	1,236
Without an allowance	870	882
Total impaired loans	2,012	2,118
Allowance for loan losses related to impaired loans	45	111
Unpaid principal balance of impaired loans	3,466	3,701
Impaired loans on nonaccrual status	955	1,032
Average impaired loans	2,078	2,189	2,311
Interest income on impaired loans	131	127	125
Interest income on impaired loans on a cash basis	$ 84	$ 80	$ 80
Home equity | Permanent Modification
Impaired loans
Rate of default for modified loans, estimated weighted-average	9.00%