CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (PARENTHETICAL) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 20	$ 21
Accumulated depreciation	$ 1,818	$ 1,737
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	474,999,478	475,582,210
Treasury stock, shares	26,891,765	26,363,033