Segment Information - Schedule of Segment Reporting Information, by Segment (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Interest expense	$ 142	$ 149	$ 422	$ 431
Operating Segments
Segment Reporting Information [Line Items]
Interest income	4	7	15	20
Interest expense	$ 13	$ 14	$ 39	$ 40