Financial Instruments and Risk Management (Tables)

3 Months Ended

Mar. 31, 2016

Financial Instruments and Risk Management [Abstract]

WTI Open Contracts

	Volumes
At March 31, 2016	(barrels per day)	Swap Prices
April – December 2016	20,000	$52.01	per barrel

Fair Value of Derivative Instruments Not Designated as Hedging Instruments

	March 31, 2016			December 31, 2015
(Thousands of dollars)	Asset (Liability) Derivatives			Asset (Liability) Derivatives
Type of Derivative Contract	Balance Sheet Location	Fair Value		Balance Sheet Location	Fair Value
Commodity	Accounts receivable	$	65,518	Accounts receivable	$	89,358
Foreign exchange	Accounts receivable		276	Accounts payable		29

Recognized Gains and Losses for Derivative Instruments Not Designated as Hedging Instruments

			Gain (Loss)
		Three Months Ended
(Thousands of dollars)		March 31,
Type of Derivative Contract	Statement of Operations Location		2016	2015
Commodity	Sales and other operating revenues	$	13,189	–
Foreign exchange	Interest and other income		305	63
		$	13,494	63

Carrying Value of Assets and Liabilities Recorded at Fair Value on Recurring Basis

	March 31, 2016					December 31, 2015
(Thousands of dollars)	Level 1		Level 2	Level 3	Total	Level 1	Level 2	Level 3	Total
Assets:
Foreign currency exchange         derivative contracts	$	–	276	–	276	–	–	–	–
Commodity derivative         contracts		–	65,518	–	65,518	–	89,358	–	89,358
	$	–	65,794	–	65,794	–	89,358	–	89,358
Liabilities:
Nonqualified employee         savings plans	$	12,628	–	–	12,628	12,971	–	–	12,971
Foreign currency exchange         derivative contracts		–	–	–	–	–	29	–	29
	$	12,628	–	–	12,628	12,971	29	–	13,000

Nonrecurring Fair Value Measurements

	March 31, 2016
						Total
					Net Book	Pretax
					Value	(Noncash)
	Fair Value				Prior to	Impairment
		Level 1	Level 2	Level 3	Impairment	Loss
(Thousands of dollars)
Assets:
Impaired proved properties
Canada	$	–	–	71,967	167,055	95,088