Financial Instruments and Risk Management (Tables)

3 Months Ended

Mar. 31, 2019

Financial Instruments and Risk Management [Abstract]

Fair Value of Derivative Instruments Not Designated as Hedging Instruments

	March 31, 2019			December 31, 2018
(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 payable	$	–	Accounts receivable	$	3,837

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		2019	2018
Commodity	Gain (loss) on crude contracts	$	–	(29,502)

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

	March 31, 2019					December 31, 2018
(Thousands of dollars)	Level 1		Level 2	Level 3	Total	Level 1	Level 2	Level 3	Total
Assets:
Commodity derivative contracts	$	–	–	–	–	–	3,837	–	3,837
	$	–	–	–	–	–	3,837	–	3,837
Liabilities:
Nonqualified employee         savings plans	$	15,436	–	–	15,436	13,845	–	–	13,845
Contingent consideration		–	–	61,260	61,260	–	–	47,730	47,730
	$	15,436	–	61,260	76,696	13,845	–	47,730	61,575