Business Segments - Summary of Operating Results by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue:
Total revenue	$ 326	$ 751	$ 1,300	$ 2,312
Operating profit (loss):
Total operating profit (loss)	(21)	14	(383)	54
United States [Member]
Revenue:
Total revenue	228	567	929	1,772
Operating profit (loss):
Total operating profit (loss)	(22)	9	(250)	44
Canada [Member]
Revenue:
Total revenue	42	83	161	243
Operating profit (loss):
Total operating profit (loss)	3	4	(60)	7
International [Member]
Revenue:
Total revenue	56	101	210	297
Operating profit (loss):
Total operating profit (loss)	$ (2)	$ 1	$ (73)	$ 3