CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (PARENTHETICAL) - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts		$ 24	$ 24
Accumulated depreciation		$ 1,642	$ 1,599
Preferred stock, par value (in dollars per share)		$ 0.01	$ 0.01
Preferred stock, shares authorized		1,000,000,000	1,000,000,000
Preferred stock, shares issued		0	0
Common stock, par value (in dollars per share)		$ 0.01	$ 0.01
Common stock, shares authorized		6,000,000,000	6,000,000,000
Common stock issued, shares		501,891,243	501,891,243
Common stock, shares outstanding		479,026,001	479,562,326
Treasury stock, shares	[1]	22,865,242	22,328,917

[1] Shares may not add due to rounding.