Shareholders' Equity - Accumulated Other Comprehensive Income (Loss) - Components and Changes of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, beginning balance	$ (1,927)	$ (1,909)	$ (1,740)	$ (1,723)
Other comprehensive (loss) income before reclassifications, net of taxes	74	(32)	128	(36)
Amounts reclassified into income, net of taxes	14	14	11	18
Tax effects reclassified into retained earnings			(103)
Accumulated other comprehensive income (loss), net of tax, ending balance	(1,839)	(1,927)	(1,704)	(1,740)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, beginning balance	(1,197)	(1,162)	(1,037)	(1,001)
Other comprehensive (loss) income before reclassifications, net of taxes	76	(35)	128	(36)
Amounts reclassified into income, net of taxes	0	0	0	0
Tax effects reclassified into retained earnings			0
Accumulated other comprehensive income (loss), net of tax, ending balance	(1,121)	(1,197)	(909)	(1,037)
Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, beginning balance	(714)	(729)	(686)	(703)
Other comprehensive (loss) income before reclassifications, net of taxes	0	3	0	0
Amounts reclassified into income, net of taxes	13	13	9	17
Tax effects reclassified into retained earnings			(99)
Accumulated other comprehensive income (loss), net of tax, ending balance	(701)	(714)	(776)	(686)
Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, beginning balance	(16)	(17)	(17)	(18)
Other comprehensive (loss) income before reclassifications, net of taxes	(2)	(1)	0	0
Amounts reclassified into income, net of taxes	1	1	2	1
Tax effects reclassified into retained earnings			(4)
Accumulated other comprehensive income (loss), net of tax, ending balance	$ (17)	$ (16)	$ (20)	$ (17)