Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Finite And Indefinite Lived Intangible Assets [Line Items]
Goodwill, impairment loss		$ 0		$ 1,004
Goodwill deductible for income tax purposes	$ 47			47
Amortization expense, intangible assets	141		$ 125	415	$ 362
Amortization expense, computer software	94		$ 73	267	$ 206
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Finite And Indefinite Lived Intangible Assets [Line Items]
Non-cash goodwill impairment charge	$ 1,004			1,004
Goodwill, impairment loss				$ 1,004