Cash Equivalents and Investments (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Cash and Cash Equivalents [Line Items]
Fair Value	$ 39	$ 3
Cash and cash equivalents	2,141	1,832
Short-term investments	90	98
Certificates of deposit and money market deposit accounts
Cash and Cash Equivalents [Line Items]
Cost	1,276	971
Gains/(Losses)	0	0
Fair Value	1,276	971
Cash and cash equivalents	1,176	866
Short-term investments	87	95
Other assets	13	10
Mutual funds
Cash and Cash Equivalents [Line Items]
Cost	46	3
Gains/(Losses)	(7)	0
Fair Value	39	3
Cash and cash equivalents	0	0
Short-term investments	3	3
Other assets	$ 36	$ 0