Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 12	$ 11
Less accumulated depreciation, depletion and amortization	$ (17,669)	$ (21,830)
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	1,925,000,000	1,925,000,000
Common stock, shares issued	937,000,000	937,000,000
Held in treasury, shares	117,000,000	118,000,000