Comprehensive Income And Accumulated Other Comprehensive Income - Changes in Components of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		$ 612
Other comprehensive income/(loss) before reclassifications		0	$ (25)	$ (256)
Amounts reclassified from AOCI		7	32	4
Other comprehensive income/(loss)		7	(13)	$ (254)
Ending balance		1,569	$ 612
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member		us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201802Member
Cumulative Effect, Period of Adoption, Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accounting Standards Update [Extensible List]				us-gaap:AccountingStandardsUpdate201802Member	us-gaap:AccountingStandardsUpdate201602Member
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ (426)	(439)	$ (426)	$ (172)
Ending balance		(432)	(439)	(426)	$ (172)
Total | Cumulative Effect, Period of Adoption, Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(20)		(20)	(2)
Ending balance				(20)	(2)
Pension and Other Retirement Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(53)	(92)	(53)	(61)
Other comprehensive income/(loss) before reclassifications		(32)	(24)	4
Amounts reclassified from AOCI		6	2	4
Other comprehensive income/(loss)		(26)	(39)	8
Ending balance		(118)	(92)	(53)	(61)
Pension and Other Retirement Benefits | Cumulative Effect, Period of Adoption, Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(17)		(17)
Ending balance				(17)
Gains / (Losses) on Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	0	0	0	1
Other comprehensive income/(loss) before reclassifications		(51)	0	(1)
Amounts reclassified from AOCI		2	0	0
Other comprehensive income/(loss)		(49)	0	(1)
Ending balance		(49)	0	0	1
Foreign Currency Translation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(406)	(401)	(406)	(113)
Other comprehensive income/(loss) before reclassifications		356	(27)	(293)
Amounts reclassified from AOCI		0	32	0
Other comprehensive income/(loss)		356	5	(293)
Ending balance		(45)	(401)	(406)	(113)
Net Investment Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	33	54	33	(1)
Other comprehensive income/(loss) before reclassifications		(273)	26	34
Amounts reclassified from AOCI		(1)	(2)	0
Other comprehensive income/(loss)		(274)	21	34
Ending balance		$ (220)	54	33	(1)
Net Investment Hedges | Cumulative Effect, Period of Adoption, Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(3)		(3)
Ending balance				(3)
Gains on Available for Sale Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 0		$ 0	2
Other comprehensive income/(loss) before reclassifications				0
Amounts reclassified from AOCI				0
Other comprehensive income/(loss)				(2)
Ending balance				0	2
Gains on Available for Sale Securities | Cumulative Effect, Period of Adoption, Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance				$ (2)
Ending balance					$ (2)