Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Allowance for doubtful accounts	$ 150	$ 129
Current portion of debt, fair value	$ 1,452	$ 1,557
Preferred stock, par or stated value per share	$ 0.01	$ 0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, shares issued	0	0
Common Class A
Common stock, par or stated value per share	$ 0.01	$ 0.01
Common stock, shares authorized	4,000,000,000	4,000,000,000
Common stock, shares issued	387,467,859	386,691,461
Common stock, shares outstanding	387,467,859	386,691,461
Common Class B
Common stock, par or stated value per share	$ 0.01	$ 0.01
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	29,381,251	29,278,424
Common stock, shares outstanding	29,381,251	29,278,424
Common Class C
Common stock, par or stated value per share	$ 0.01	$ 0.01
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	0	0