Business Segments - Summary of Operating Results by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue:
Total revenue	$ 651	$ 501	$ 1,282	$ 1,049
Operating profit (loss):
Total operating loss	$ (14)	$ (57)	$ (35)	$ (122)
Operating profit (loss) % of revenue:
Total operating loss %	(2.20%)	(11.40%)	(2.70%)	(11.60%)
United States [Member]
Revenue:
Total revenue	$ 481	$ 337	$ 920	$ 694
Operating profit (loss):
Total operating loss	$ (16)	$ (44)	$ (42)	$ (103)
Operating profit (loss) % of revenue:
Total operating loss %	(3.30%)	(13.10%)	(4.60%)	(14.80%)
Canada [Member]
Revenue:
Total revenue	$ 79	$ 55	$ 175	$ 118
Operating profit (loss):
Total operating loss	$ 2	$ (8)	$ 5	$ (14)
Operating profit (loss) % of revenue:
Total operating loss %	2.50%	(14.50%)	2.90%	(11.90%)
International [Member]
Revenue:
Total revenue	$ 91	$ 109	$ 187	$ 237
Operating profit (loss):
Total operating loss		$ (5)	$ 2	$ (5)
Operating profit (loss) % of revenue:
Total operating loss %	0.00%	(4.60%)	1.10%	(2.10%)