CONSOLIDATED BALANCE SHEETS (PARENTHETICAL) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 21	$ 24
Accumulated depreciation	$ 1,737	$ 1,599
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	501,900,000	501,900,000
Common stock, shares outstanding	475,528,210	479,562,326
Treasury shares	26,400,000	22,300,000