Loans and Allowance for Loan Losses - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Loans disclosures
Accrued interest	$ 241		$ 241
(Reversal of) provision for loan losses	353	$ 66	801	$ 125
Commercial
Loans disclosures
(Reversal of) provision for loan losses	264	20	538	52
Consumer
Loans disclosures
(Reversal of) provision for loan losses	89	$ 51	263	$ 78
Impact from COVID-19
Loans disclosures
Allowance for uncollectible receivables	$ 5		5
Impact from COVID-19 | Commercial
Loans disclosures
Loan restructuring, modifications, amount			2,700
Impact from COVID-19 | Consumer
Loans disclosures
Loan restructuring, modifications, amount			$ 3,800