Cash Equivalents and Investments (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 2,809	$ 2,597
Short-term investments	88	99
Certificates of deposit and money market deposit accounts
Cash and Cash Equivalents [Line Items]
Cost	1,481	1,430
Gains/(Losses)	0	0
Fair Value	1,481	1,430
Cash and cash equivalents	1,370	1,325
Short-term investments	88	99
Other assets	23	6
Mutual funds
Cash and Cash Equivalents [Line Items]
Cost	53	54
Gains/(Losses)	7	6
Fair Value	60	60
Cash and cash equivalents	0	0
Short-term investments	0	0
Other assets	$ 60	$ 60