Consolidated Balance Sheet (Parenthetical) - USD ($) shares in Millions, $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts receivable, current	$ 18	$ 14
6.875% Mandatory Convertible Preferred Stock, Par or Stated Value Per Share (dollars per share)	$ 0.01	$ 0.01
6.875% Mandatory Convertible Preferred Stock, Shares Authorized	20	20
6.875% Mandatory Convertible Preferred Stock, shares issued	2	2
Convertible Preferred Stock, shares outstanding	2	2
Mandatory redemption and aggregate liquidation value, 6.875% Mandatory Convertible Preferred Stock	$ 1,650	$ 1,650
Common stock, par value (dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	600	600
Common stock, shares issued	416	415
Common stock, shares outstanding	416	415