CONSOLIDATED BALANCE SHEETS (PARENTHETICAL) - USD ($) $ in Millions		Dec. 31, 2018		Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts		$ 24		$ 25
Accumulated depreciation		$ 1,599		$ 1,471
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		501,891,243	[1]	501,891,243
Common stock, shares outstanding		479,562,326		486,130,461
Treasury shares	[1]	22,328,917		15,760,782.000

[1] Shares may not add due to rounding.