Accumulated Other Comprehensive Income (Loss) - Schedule of Accumulated Other Comprehensive Income (Loss), Net of Tax (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 9,655	$ 10,690	$ 13,716
Other comprehensive income (loss) before reclassifications	30	(75)
Amounts reclassified out of accumulated other comprehensive income (loss)	(4)	13
Income tax effects	16	14
Total other comprehensive income (loss)	42	(48)	(57)
Ending balance	9,151	9,655	10,690
Currency translation differences
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	203	218
Other comprehensive income (loss) before reclassifications	78	(15)
Amounts reclassified out of accumulated other comprehensive income (loss)	0	0
Income tax effects	0	0
Total other comprehensive income (loss)	78	(15)
Ending balance	281	203	218
Change in fair value cash flow hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	2	(3)
Other comprehensive income (loss) before reclassifications	15	(6)
Amounts reclassified out of accumulated other comprehensive income (loss)	(4)	13
Income tax effects	(2)	(2)
Total other comprehensive income (loss)	9	5
Ending balance	11	2	(3)
Net actuarial gain/(losses)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(130)	(92)
Other comprehensive income (loss) before reclassifications	(63)	(54)
Amounts reclassified out of accumulated other comprehensive income (loss)	0	0
Income tax effects	18	16
Total other comprehensive income (loss)	(45)	(38)
Ending balance	(175)	(130)	(92)
Accumulated Other Comprehensive Income (loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	75	123	177
Total other comprehensive income (loss)	42	(48)	(57)
Ending balance	$ 117	$ 75	$ 123