Derivatives - Gains/(Losses) on Derivatives Associated with Cash Flow Hedges (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) expected to be reclassified to earnings in the next twelve months	$ 28
Cash Flow Hedges | Hedging Instruments And Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss), cash flow hedges	15	$ 11	$ (6)
Variability in cash flows related to debt instruments (primarily loans)	(6)	4	2
Cash Flow Hedges | Hedging Instruments And Hedged Items | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss), cash flow hedges	$ 3	$ 21	$ (6)