Financial Instruments Cross-currency forward-exchange contracts (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Foreign Currency Fair Value Hedge Derivative [Line Items]
Unrealized gains/(losses) on derivatives for net investment hedges, net	$ 16	$ (30)	$ 33	$ (27)
Derivatives Designated as Hedging Instruments: | Forward-starting interest rate swap contracts
Foreign Currency Fair Value Hedge Derivative [Line Items]
Unrealized gains/(losses) on derivatives for net investment hedges, net	1	5	20	(22)
Derivatives Designated as Hedging Instruments: | Cross-currency interest rate swap contracts
Foreign Currency Fair Value Hedge Derivative [Line Items]
Unrealized gains/(losses) on derivatives for net investment hedges, net	$ 16	$ (30)	$ 33	$ (27)