CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Mar. 31, 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)	5,603,458	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	911,794,424	908,732,809
Treasury stock, common shares	3,416,465	2,240,394
VIE, cash and cash equivalents	$ 4	$ 5
VIE. proved oil and natural gas properties	69,284	68,858
VIE. accumulated depreciation, depletion and amortization	(63,903)	(63,664)
VIE. other current liabilities	1,357	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	(462)	(461)
VIE. other current liabilities	$ 3	$ 3