Cash Equivalents and Investments (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Line Items]
Fair Value	$ 58	$ 60
Cash and cash equivalents	2,239	2,597
Short-term investments	104	99
Other assets	636	515
Certificates of deposit and money market deposit accounts
Cash and Cash Equivalents [Line Items]
Cost	1,004	1,430
Gains/(Losses)	0	0
Fair Value	1,004	1,430
Cash and cash equivalents	891	1,325
Short-term investments	104	99
Other assets	9	6
Mutual funds
Cash and Cash Equivalents [Line Items]
Cost	50	54
Gains/(Losses)	8	6
Fair Value	58	60
Cash and cash equivalents	0	0
Short-term investments	0	0
Other assets	$ 58	$ 60