CONSOLIDATED BALANCE SHEETS (PARENTHETICAL) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts		$ 25	$ 30
Accumulated depreciation		$ 1,471	$ 1,358
Preferred stock, par value (in dollars per share)		$ 0.01	$ 0.01
Preferred stock, authorized (in shares)		1,000,000,000	1,000,000,000
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, shares issued	[1]	501,891,243	501,891,243
Common stock, shares outstanding		486,130,461	492,855,297
Treasury shares	[1]	15,760,782	9,035,946.000

[1] Shares may not add due to rounding.