Other Comprehensive Loss - Components of Accumulated Other Comprehensive Loss (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Unrealized gains (losses) on available-for-sale securities, tax benefit			$ 2
Unrealized gains (losses) on available-for-sale securities, tax expense	$ 3	$ 4
Foreign currency translation adjustments, income tax benefit			8
Foreign currency translation adjustments, income tax expense	6	5
Defined benefit plans, income tax benefit	16	14
Defined benefit plans, income tax expense			10
Change in fair value of derivative instruments, income tax benefit	15	13
Change in fair value of derivative instruments, income tax expense			5
Defined benefit plans, benefit reclassified into operations from other comprehensive income	6	3	5
Interest expense on derivative instruments, benefit reclassified into operations from other comprehensive income	$ 5
Interest benefit on derivative instruments, expense reclassified into operations from other comprehensive income		$ 3	$ 2