Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Doubtful accounts and allowances	$ 44	$ 46
Accumulated depreciation	$ 13,514	$ 13,663
Convertible preferred stock, par value (in dollars per share)	$ 100	$ 100
Convertible preferred stock, shares authorized (in shares)	3,100	3,100
Convertible preferred stock, shares issued (in shares)	2,300	2,300
Common stock, par value (in dollars per share)	$ 0.50	$ 0.50
Common stock, shares authorized (in shares)	3,800,000,000	3,800,000,000
Common stock, shares issued (in shares)	1,729,000,000	1,726,000,000
Treasury stock, shares held (in shares)	961,000,000	961,000,000