Derivative Financial Instruments And Hedging Activities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Average maturity of foreign currency forward contracts, in years	2 years
Cash and equivalents	$ 2,824,000,000	$ 902,000,000	[1]
Marketable securities held in trust	211,000,000	207,000,000
Derivative notional amount	$ 9,400,000,000	$ 5,000,000,000
Maximum
Derivative Instruments, Gain (Loss) [Line Items]
Maturity of fixed-income securities, in years	5 years

[1] *Prior-period information has been restated for the retrospective application of a change in accounting principle related to the amortization of actuarial gains and losses for our qualified U.S. government pension plans, which we adopted in the fourth quarter of 2020. For further discussion of this change in accounting principle, see Note T to the Consolidated Financial Statements.