Financial Instruments and Risk Management (Tables)

12 Months Ended

Dec. 31, 2019

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Fair Value of Derivative Instruments Not Designated as Hedging Instruments

At December 31, 2019 and 2018, the fair value of derivative instruments not designated as hedging instruments are presented in the following table.  

	December 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	$	(33,364	)	Accounts receivable	$	3,837

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

For the years ended December 31, 2019, 2018, and 2017, 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	2019			2018		2017
Commodity	Gain (loss) on crude contracts	$	(856	)	(41,975	)	9,566