Business Segments - Summary of Operating Results by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenue:
Total revenue	$ 520	$ 753	$ 1,569	$ 2,366
Operating profit (loss):
Total operating loss	$ (53)	$ (291)	$ (175)	$ (326)
Operating profit (loss) % of revenue:
Total operating loss %	(10.20%)	(38.60%)	(11.20%)	(13.80%)
United States [Member]
Revenue:
Total revenue	$ 372	$ 497	$ 1,066	$ 1,594
Operating profit (loss):
Total operating loss	$ (46)	$ (294)	$ (149)	$ (329)
Operating profit (loss) % of revenue:
Total operating loss %	(12.40%)	(59.20%)	(14.00%)	(20.60%)
Canada [Member]
Revenue:
Total revenue	$ 67	$ 94	$ 185	$ 299
Operating profit (loss):
Total operating loss	$ (2)	$ 2	$ (16)
Operating profit (loss) % of revenue:
Total operating loss %	(3.00%)	2.10%	(8.60%)	0.00%
International [Member]
Revenue:
Total revenue	$ 81	$ 162	$ 318	$ 473
Operating profit (loss):
Total operating loss	$ (5)	$ 1	$ (10)	$ 3
Operating profit (loss) % of revenue:
Total operating loss %	(6.20%)	0.60%	(3.10%)	0.60%