Employee Stock Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Benefits Disclosure [Line Items]
Compensation expense	$ 17	$ 15	$ 14
Granted	2,200,000	1,400,000	1,200,000
Vested	1,200,000	900,000	800,000
RSU Awards | Executive Officer
Employee Benefits Disclosure [Line Items]
Compensation expense	$ 15	$ 13	$ 12
RSU Awards | Vesting over one-year Period
Employee Benefits Disclosure [Line Items]
Vesting term	1 year
RSU Awards | Vesting over two-year Period
Employee Benefits Disclosure [Line Items]
Vesting term	2 years
RSU Awards | Vesting over three-year Period
Employee Benefits Disclosure [Line Items]
Vesting term	3 years
RSU Awards | Time-Based Awards
Employee Benefits Disclosure [Line Items]
Vesting term	3 years
Percentage of total shares awarded	40.00%
Percentage of shares expected to be released	100.00%
RSU Awards | TSR Awards
Employee Benefits Disclosure [Line Items]
Vesting term	3 years
Percentage of total shares awarded	30.00%
RSU Awards | Performance-Based Awards
Employee Benefits Disclosure [Line Items]
Percentage of total shares awarded	30.00%
RSU Awards | TSR Awards, Performance Period Three
Employee Benefits Disclosure [Line Items]
Performance period	3 years
Other Stock Plans, Upper-middle management awards
Employee Benefits Disclosure [Line Items]
Vesting term	3 years
Other Stock Plans, employee stock purchase plan
Employee Benefits Disclosure [Line Items]
Employee stock purchase plan discount percentage	10.00%
Other Stock Plans
Employee Benefits Disclosure [Line Items]
Compensation expense	$ 2	$ 2	$ 2
Granted	200,000	100,000	100,000
2020 Comprehensive Plan
Employee Benefits Disclosure [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	15,000,000
Senior Executive Plan | RSU Awards
Employee Benefits Disclosure [Line Items]
Granted	2,000,000.0
Unvested RSUs	1,500,000
Unrecognized compensation cost related to unvested RSU awards	$ 11
Senior Executive Plan | RSU Awards | Vesting over one-year Period
Employee Benefits Disclosure [Line Items]
Vesting term	1 year
Senior Executive Plan | RSU Awards | Vesting over two-year Period
Employee Benefits Disclosure [Line Items]
Vesting term	2 years
Senior Executive Plan | RSU Awards | Vesting over three-year Period
Employee Benefits Disclosure [Line Items]
Vesting term	3 years