Consolidated Balance Sheets Parentheticals - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Consolidated Balance Sheets Parenthetical [Abstract]
Allowance for doubtful accounts	$ 12	$ 6
Less accumulated depreciation, depletion and amortization	$ (21,564)	$ (20,255)
Preferred stock, no par value	$ 0	$ 0
Preferred stock, shares authorized	26,000,000	26,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value per share	$ 1	$ 1
Common stock, shares authorized	1,100,000,000	1,100,000,000
Common stock, shares issued	937,000,000	937,000,000
Held in treasury, shares	87,000,000	90,000,000