Goodwill and Other Intangible Assets - Changes in the Carrying Amount of Goodwill by Reporting Segment (Parenthetical) (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2019	[1]
Goodwill And Intangible Assets Disclosure [Abstract]
Adjustments to finalize purchase accounting estimates		$ 107	$ 61	$ 168
Cumulative impairment charges	$ 2,200		$ 0

[1] Includes adjustments of $61 million and $107 million identified in the first and second quarters of 2019, respectively. See Note 3, Business Combination for further discussion.