Goodwill and Other Intangible Assets - Changes in the Carrying Amount of Goodwill by Reporting Segment (Parenthetical) (Detail) $ in Billions	Mar. 31, 2019 USD ($)
Goodwill And Intangible Assets Disclosure [Abstract]
Cumulative impairment charges	$ 2.2

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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