Cash Equivalents and Investments (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Line Items]
Fair Value	$ 3	$ 33
Cash and cash equivalents	1,832	1,685
Short-term investments	98	133
Money market mutual funds
Cash and Cash Equivalents [Line Items]
Cost		15
Gross Unrealized Gains		0
Fair Value		15
Cash and cash equivalents		15
Short-term investments		0
Other assets		0
Certificates of deposit and money market deposit accounts
Cash and Cash Equivalents [Line Items]
Cost	971	1,022
Gross Unrealized Gains	0	0
Fair Value	971	1,022
Cash and cash equivalents	866	904
Short-term investments	95	116
Other assets	10	2
Open ended mutual funds
Cash and Cash Equivalents [Line Items]
Cost	3	29
Gross Unrealized Gains	0	4
Fair Value	3	33
Cash and cash equivalents	0	0
Short-term investments	3	17
Other assets	$ 0	$ 16