INVESTMENTS (Tables)

6 Months Ended

Jun. 30, 2013

Investments Debt And Equity Securities [Abstract]

Components of Investments

Investments consisted of the following as of June 30, 2013:

			Unrealized		Unrealized			Fair
	Cost Basis		Gains		Losses			Value
	(Thousands of dollars)
Investments:
Money Market Mutual Funds	$	32,721	$	—	$	—		$	32,721
Commercial Paper		25,740		2		(6	)		25,736
Corporate bonds and notes		32,486		1		(45	)		32,442
Subtotal		90,947		3		(51	)		90,899
Deferred compensation plan assets included in other assets		1,888		—		—			1,888
Total	$	92,835	$	3	$	(51	)	$	92,787

Investments consisted of the following as of December 31, 2012:

			Unrealized		Unrealized			Fair
	Cost Basis		Gains		Losses			Value
	(Thousands of dollars)
Investments:
Money Market Mutual Funds	$	29,816	$	—	$	—		$	29,816
Commercial Paper		5,494		1		(2	)		5,493
Corporate bonds and notes		29,986		2		(11	)		29,977
Subtotal		65,296		3		(13	)		65,286
Deferred compensation plan assets included in other assets		2,687		—		—			2,687
Total	$	67,983	$	3	$	(13	)	$	67,973

Cost and Fair Value of Debt Investments Based on Maturities

The following table presents the cost and fair value of our debt investments based on maturities as of:

	June 30, 2013				December 31, 2012
	Amortized		Fair		Amortized		Fair
	Costs		Value		Costs		Value
	(Thousands of dollars)
Due in one year or less	$	43,282	$	43,259	$	35,480	$	35,470
Due within two years		14,944		14,919		—		—
Total	$	58,226	$	58,178	$	35,480	$	35,470

Average Coupon Rate Percentage and Average Days to Maturity of Debt

The following table presents the average coupon rate percentage and the average days to maturity of our debt investments as of:

	June 30, 2013				December 31, 2012
	Average		Average		Average		Average
	Coupon		Days To		Coupon		Days To
	Rate (%)		Maturity		Rate (%)		Maturity
Commercial Paper		0.138		95		0.305		138
Corporate bonds and notes		2.634		342		2.965		112

Investments in Continuous Unrealized Loss Position for Less Than Twelve Months

The following table presents the fair value and unrealized losses related to our investments that have been in a continuous unrealized loss position for less than twelve months as of:

	June 30, 2013					December 31, 2012
			Unrealized					Unrealized
	Fair Value		Losses			Fair Value		Losses
	(Thousands of dollars)
Commercial Paper	$	17,737	$	(6	)	$	2,494	$	(2	)
Corporate bonds and notes		28,935		(45	)		16,771		(11	)
Total	$	46,672	$	(51	)	$	19,265	$	(13	)

Investments in Continuous Unrealized Loss Position for Twelve Months or More

The following table presents the fair value and unrealized losses related to our investments that have been in a continuous unrealized loss position for twelve months or more as of:

	June 30, 2013				December 31, 2012
			Unrealized				Unrealized
	Fair Value		Losses		Fair Value		Losses
	(Thousands of dollars)
Corporate bonds and notes	$	—	$	—	$	2,004	$	(.4	)
	$	—	$	—	$	2,004	$	(.4	)