Derivatives - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Valuation adjustments related to the credit risk associated with counterparties of customer accomodation derivative contracts	$ 21	$ 3
Notional amount of the risk participation agreements	4,345	4,002
Amount of variation margin payment applied to derivative asset contracts	748	249
Amount of variation margin payment applied to derivative liability contracts	528	23
Total collateral
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	1,100	481
Derivative Liability, Fair Value, Amount Offset Against Collateral	$ 241	551
Interest Rate Contract | Credit Risk
Derivative [Line Items]
Credit Risk Derivatives Average Remaining Life	3 years 6 months
Fair value of risk participation agreements	$ 9	8
Interest Rate Contract | Cash Flow Hedging
Derivative [Line Items]
Maximum length of time hedged in cash flow hedge	63 months
Deferred gains or losses, net of tax, on cash flow hedges were recorded in accumulated other comprehensive income	$ 519	$ 160
Net deferred gains or losses, net of tax, recorded in accumulated other comprehensive income are expected to be reclassified into earnings during the next twelve months	$ 10