Derivatives - Gains/(Losses) on Derivatives Associated with Cash Flow Hedges (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) expected to be reclassified to earnings in the next twelve months			$ 22
Hedging Instruments And Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss), cash flow hedges	$ 0	$ 2	(1)	$ 15
Gain (loss) reclassified from AOCI into interest income	(2)	(2)	(3)	(2)
Hedging Instruments And Hedged Items | Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss), cash flow hedges	$ (6)	$ 0	$ (14)	$ 17