Combined Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 1	$ 2
Variable interest entities - assets	245	239
Variable interest entities - liabilities	$ 222	$ 262
Common stock, par value (per share)	$ 0.01
Common stock, authorized shares	6,000,000,000
Common stock, issued shares	214,873,778
Common stock, outstanding shares	214,845,244