Financial Instruments (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Dec. 31, 2020
Short-Term Investments [Abstract]
Short-term investments	$ 46	$ 46	$ 60
Fair Value of Debt Instruments [Abstract]
Fair value of total debt	32,800	32,800	31,900
Fair value of total debt in excess of (less than) carrying value	3,400	3,400	$ 5,100
Equity Securities, FV-NI, Gain (Loss) [Abstract]
Unrealized gain (loss) on fair value of equity investments	(12)	8
Significant Other Observable Inputs (Level 2) [Member] | Time Deposits [Member]
Short-Term Investments [Abstract]
Short-term investments	$ 46	$ 46