Cash Equivalents and Investments (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Line Items]
Fair Value	$ 55	$ 60
Cash and cash equivalents	2,769	2,597
Short-term investments	96	99
Certificates of deposit and money market deposit accounts
Cash and Cash Equivalents [Line Items]
Cost	1,639	1,430
Gains/(Losses)	0	0
Fair Value	1,639	1,430
Cash and cash equivalents	1,531	1,325
Short-term investments	96	99
Other assets	12	6
Mutual funds
Cash and Cash Equivalents [Line Items]
Cost	49	54
Gains/(Losses)	6	6
Fair Value	55	60
Cash and cash equivalents	0	0
Short-term investments	0	0
Other assets	$ 55	$ 60