Comprehensive Income And Accumulated Other Comprehensive Loss - Changes in Components of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accounting Standards Update [Extensible List]					us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201802Member
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			$ 612
Ending balance	$ 1,497		1,497		$ 612
Pension and Other Retirement Benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(84)	$ (70)	(92)	$ (53)	(53)
Other comprehensive income/(loss) before reclassifications	(7)	0	(1)	(1)
Amounts reclassified from AOCL	2	1	4	2
Other comprehensive income/(loss)	(5)	1	3	(16)
Ending balance	(89)	(69)	(89)	(69)	(92)	$ (53)
Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(49)	0	0	0	0
Other comprehensive income/(loss) before reclassifications	0	0	(50)	0
Amounts reclassified from AOCL	0	0	1	0
Other comprehensive income/(loss)	0	0	(49)	0
Ending balance	(49)	0	(49)	0	0	0
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(479)	(401)	(401)	(406)	(406)
Other comprehensive income/(loss) before reclassifications	186	(193)	108	(188)
Amounts reclassified from AOCL	0	0	0	0
Other comprehensive income/(loss)	186	(193)	108	(188)
Ending balance	(293)	(594)	(293)	(594)	(401)	(406)
Net Investment Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	70	25	54	33	33
Other comprehensive income/(loss) before reclassifications	(143)	102	(127)	97
Amounts reclassified from AOCL	0	(1)	0	(1)
Other comprehensive income/(loss)	(143)	101	(127)	93
Ending balance	(73)	126	(73)	126	54	33
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(542)	(446)	(439)	(426)	(426)
Other comprehensive income/(loss) before reclassifications	36	(91)	(70)	(92)
Amounts reclassified from AOCL	2	0	5	1
Other comprehensive income/(loss)	38	(91)	(65)	(111)
Ending balance	$ (504)	$ (537)	$ (504)	(537)	(439)	(426)
Cumulative Effect, Period of Adoption, Adjustment | Pension and Other Retirement Benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance				(17)	(17)
Ending balance						(17)
Cumulative Effect, Period of Adoption, Adjustment | Net Investment Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance				(3)	(3)
Ending balance						(3)
Cumulative Effect, Period of Adoption, Adjustment | Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance				$ (20)	$ (20)
Ending balance						$ (20)