Consolidated Balance Sheets Parentheticals - USD ($) shares in Millions, $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Consolidated Balance Sheets Parenthetical [Abstract]
Allowance for Doubtful Accounts Receivable, Current	$ 4	$ 4
Less accumulated depreciation, depletion and amortization	$ (22,763)	$ (23,260)
Preferred stock, no par value	$ 0	$ 0
Preferred stock shares authorized	26	26
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	1,100
Common stock, shares issued	937	770
Common stock, securities exchangeable, no par value	$ 0	$ 0
Common stock, securities exchangeable, shares authorized	29	29
Common stock, securities exchangeable, shares issued	0	0
Common stock, securities exchangeable, shares outstanding	0	0
Common stock, held in treasury, shares	89	93