Investments (Tables)

6 Months Ended

Jun. 30, 2019

Investments Debt And Equity Securities [Abstract]

Components of Investments

Investments consisted of the following as of June 30, 2019:

	Cost Basis		Unrealized Gains		Unrealized Losses		Fair Value
	(Thousands of dollars)
Investments:
Money market mutual funds	$	88,217	$	—	$	—	$	88,217
Deferred compensation plan assets included in other assets		889		—		—		889
Total	$	89,106	$	—	$	—	$	89,106

Investments consisted of the following as of December 31, 2018:

	Cost Basis		Unrealized Gains		Unrealized Losses		Fair Value
	(Thousands of dollars)
Investments:
Money market mutual funds	$	26,308	$	—	$	—	$	26,308
Deferred compensation plan assets included in other assets		772		—		—		772
Total	$	27,080	$	—	$	—	$	27,080