Revenue from Contracts with Customers - Contract Liabilities (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2018
Change in Contract with Customer, Liability [Roll Forward]
Balance at December 31, 2017		$ 37
Increase due to cumulative effect of adopting Topic 606		98
Increase due to cash received, excluding revenues recognized in the period (1)	$ 12	52
Decrease due to revenue recognized (2)	(9)	(21)
Balance at June 30, 2018	166	166
Contract liabilities at June 30, 2018
Other current liabilities			$ 37
Other long-term liabilities - other			129
Total contract liabilities from contracts with customers	$ 166	$ 37	$ 166