Derivatives - Gains/(Losses) on Derivatives Associated with Cash Flow Hedges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) expected to be reclassified to earnings in the next twelve months			$ 20
Hedging Instruments And Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss), cash flow hedges	$ 0	$ (1)	(1)	$ 14
Gain (loss) reclassified from AOCI into interest income	(1)	(2)	(4)	(4)
Hedging Instruments And Hedged Items | Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss), cash flow hedges	$ (6)	$ (8)	$ (20)	$ 10