Financial Instruments and Risk Management (Tables)

12 Months Ended

Dec. 31, 2020

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Fair Value of Derivative Instruments Not Designated as Hedging Instruments

At December 31, 2020 and 2019, the fair value of derivative instruments not designated as hedging instruments are presented in the following table.  

	December 31, 2020			December 31, 2019
(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	$	13,050	Accounts payable	$	(33,364)
	Accounts payable	(89,842)
	Deferred credits and other liabilities	(12,833)

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

For the years ended December 31, 2020, 2019, and 2018, the gains and losses recognized in the Consolidated Statements of Operations for derivative instruments not designated as hedging instruments are presented in the following table.

		Gain (Loss)
(Thousands of dollars)		Year Ended December 31,
Type of Derivative Contract	Statement of Operations Locations	2020		2019	2018
Commodity	(Loss) gain on crude contracts	$	202,661	(856)	(41,975)