Consolidated Statement Of Earnings - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Statement Of Earnings [Abstract]
Product revenues	$ 2,999	$ 2,443	$ 3,350
Gains (losses) from risk management, net	482	(275)	592
Market optimization	863	647	368
Other	99	103	112
Total Revenues	4,443	2,918	4,422
Expenses
Production, mineral and other taxes	112	99	144
Transportation and processing	845	901	1,252
Operating	506	598	723
Purchased product	788	586	323
Depreciation, depletion and amortization	833	859	1,488
Impairments		1,396	6,473
Accretion of asset retirement obligation	37	51	45
Administrative	254	309	275
Total Operating Expenses	3,375	4,799	10,723
Operating Income (Loss)	1,068	(1,881)	(6,301)
Interest	363	397	614
Foreign exchange (gain) loss, net	(279)	(210)	1,082
(Gain) loss on divestitures, net	(404)	(390)	(14)
Other (gains) losses, net	(42)	(58)	27
Total Other (Income) Expenses	(362)	(261)	1,709
Net Earnings (Loss) Before Income Tax	1,430	(1,620)	(8,010)
Income tax expense (Recovery)	603	(676)	(2,845)
Net Earnings (Loss)	$ 827	$ (944)	$ (5,165)
Net Earnings (Loss) per Common Share
Earnings Per Share, Basic and Diluted	$ 0.85	$ (1.07)	$ (6.28)
Dividends, Common Stock [Abstract]
Common Stock, Dividends, Per Share, Cash Paid	$ 0.06	$ 0.06	$ 0.28
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Weighted Average Number of Shares Outstanding, Basic and Diluted	973,100,000	882,600,000	822,100,000