CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Preferred stock, par value (usd per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (shares)	20,000,000	20,000,000
Preferred stock, shares outstanding (shares)	5,603,468	5,603,458
Common stock, par value (usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized	2,000,000,000	2,000,000,000
Common stock, shares issued	913,691,662	908,732,809
Treasury stock, common shares	3,307,953	2,240,394
VIE, cash and cash equivalents	$ 4	$ 5
VIE, proved oil and natural gas properties	70,620	68,858
VIE, accumulated depreciation, depletion and amortization	(64,500)	(63,664)
VIE, other current liabilities	1,438	1,455
Variable Interest Entities, Primary Beneficiary [Member]
VIE, cash and cash equivalents	1	2
VIE, proved oil and natural gas properties	488	488
VIE, accumulated depreciation, depletion and amortization	(463)	(461)
VIE, other current liabilities	$ 2	$ 3