Assets and Liabilities Measured at Fair Value (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

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

The fair value measurements for these assets and liabilities at December 31, 2019 and 2018 are presented in the following table

	December 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	$	17,035	—	—	17,035	13,845	—	—	13,845
Commodity derivative contracts	—		33,364	—	33,364	—	—	—	—
Contingent consideration	—		—	146,787	146,787	—	—	47,730	47,730
	$	17,035	33,364	146,787	197,186	13,845	—	47,730	61,575

Carrying Amounts and Estimated Fair Values of Financial Instruments

The following table presents the carrying amounts and estimated fair values of financial instruments held by the Company at December 31, 2019 and 2018.  The fair value of a financial instrument is the amount at which the instrument could be exchanged in a current transaction between willing parties.  The table excludes cash and cash equivalents, trade accounts receivable, trade accounts payable and accrued expenses, all of which had fair values approximating carrying amounts.  The fair value of current and long-term debt was estimated based on rates offered to the Company at that time for debt of the same

maturities.  The Company has off-balance sheet exposures relating to certain letters of credit.  The fair value of these, which represents fees associated with obtaining the instruments, was nominal.

	December 31,
	2019					2018
(Thousands of dollars)	Carrying Amount			Fair Value		Carrying Amount		Fair Value
Financial assets (liabilities):
Current and long-term debt	$	(2,803,381	)	(3,074,929	)	(3,109,986	)	(2,899,912	)

Nonrecurring Fair Value Measurements

The fair value information associated with these impaired properties is presented in the following table

	Year Ended December 31, 2018
					Net Book Value Prior to Impairment	Total Pretax Impairment
	Fair Value
(Thousands of dollars)	Level 1		Level 2	Level 3
Assets:
Impaired proved properties
United States Midland	$	—	—	37,690	57,690	20,000