Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Measurements [Abstract]

Schedule Of Fair Value, Assets And Liabilities Measured On Recurring Basis

As at December 31, 2017		Level 1 Quoted Prices in Active Markets		Level 2 Other Observable Inputs		Level 3 Significant Unobservable Inputs		Total Fair Value		Netting (1)		Carrying Amount
Risk Management Assets
Commodity Derivatives:
Current assets	$	-	$	189	$	-	$	189	$	(15)	$	174
Long-term assets		-		248		-		248		(2)		246
Foreign Currency Derivatives:
Current assets		-		31		-		31		-		31
Risk Management Liabilities
Commodity Derivatives:
Current liabilities		3		196		51		250		(15)		235
Long-term liabilities		-		15		-		15		(2)		13
Foreign Currency Derivatives:
Current liabilities		-		1		-		1		-		1
Other Derivative Contracts
Current in accounts payable and accrued liabilities	$	-	$	5	$	-	$	5	$	-	$	5
Long-term in other liabilities and provisions		-		14		-		14		-		14
As at December 31, 2016		Level 1 Quoted Prices in Active Markets		Level 2 Other Observable Inputs		Level 3 Significant Unobservable Inputs		Total Fair Value		Netting (1)		Carrying Amount
Risk Management Assets
Commodity Derivatives
Current assets	$	-	$	11	$	-	$	11	$	(11)	$	-
Long-term assets		-		19		-		19		(3)		16
Risk Management Liabilities
Commodity Derivatives:
Current liabilities		-		228		36		264		(11)		253
Long-term liabilities		-		38		-		38		(3)		35
Foreign Currency Derivatives:
Current liabilities		-		1		-		1		-		1
Other Derivative Contracts
Current in accounts payable and accrued liabilities	$	-	$	5	$	-	$	5	$	-	$	5
Long-term in other liabilities and provisions		-		14		-		14		-		14

Summary Of Changes In Level 3 Fair Value Measurements

		Risk Management
		2017		2016
Balance, Beginning of Year	$	(36)	$	16
Total Gains (Losses)		(21)		(16)
Purchases, Sales, Issuances and Settlements:
Purchases, sales and issuances		-		-
Settlements		6		(26)
Transfers Out of Level 3 (1)		-		(10)
Balance, End of Year	$	(51)	$	(36)
Change in Unrealized Gains (Losses) Related to Assets and Liabilities Held at End of Year	$	(51)	$	(27)

Quantitative Information About Unobservable Inputs Used In Level 3

As at December 31	Valuation Technique	Unobservable Input	2017	2016
Risk Management - WTI Options	Option Model	Implied Volatility	17% - 76%	18% - 64%