Income Taxes - Difference Between Effective Tax Rate (Detail) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income tax provision (benefit) at federal statutory rate				$ (18)	$ (81)	$ (181)
Foreign tax rate differential				(2)	2	(1)
State income tax provision (benefit), net of federal benefit				(5)	(3)	(8)
Nondeductible expenses				2	8	3
Foreign tax credits				(31)	(2)	(3)
Nondeductible goodwill impairment						42
One-time transition tax				33
U.S. tax rate change				69
Change in valuation allowance				(45)	78	129
Change in contingency reserve and other				$ (3)	2	3
Income tax provision (benefit)	$ 23	$ (15)	$ (4)		$ 4	$ (16)
Effective tax rate				0.00%	(1.60%)	3.00%