Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income tax (benefit) expense	$ (84)	$ 23	$ (63)	$ 34
Effective income tax rate	215.40%	38.30%	393.80%	35.40%
Non-deductible transaction costs	$ 16		$ 16
Changs in other valuation allowances	12		19
State tax and other items	15		15
Provision for income tax benefit at statutory income tax rate	117		$ 117
Unrecognized tax benefits Increased during the period	$ 17