Segment Information - Schedule of Segment Reporting Information, by Segment (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Interest expense	$ 144	$ 142	$ 287	$ 281
Operating Segments
Segment Reporting Information [Line Items]
Interest income	1	6	4	11
Interest expense	$ 9	$ 14	$ 21	$ 27