Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Trade accounts receivable allowance	$ 132	$ 104
Common stock par value	$ 0.01	$ 0.01
Common stock shares authorized	2,000,000,000.0	2,000,000,000.0
Common stock shares issued	851,300,000	835,500,000
Common stock shares outstanding	711,000,000.0	695,500,000
Preferred stock
Preferred stock, no par value	$ 0	$ 0
Preferred stock, shares authorized	15,000,000.0	15,000,000.0
Preferred stock | Series A Preferred Stock
Preferred stock, shares outstanding	1,650,000	1,650,000
Preferred stock, shares issued	1,650,000	1,650,000
Preferred stock, dividend rate, percentage	4.75%	4.75%
Preferred stock | Series B Preferred Stock
Preferred stock, shares outstanding	1,720,000	0
Preferred stock, shares issued	1,720,000	0
Preferred stock, dividend rate, percentage	5.00%