INVESTMENTS (Tables)

3 Months Ended

Mar. 31, 2014

Investments Debt And Equity Securities [Abstract]

Components of Investments

Investments consisted of the following as of March 31, 2014:

	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(Thousands of dollars)
Investments:
Money Market Mutual Funds	$	77,130	$	—	$	—		$	77,130
Municipal bonds and notes		1,500		2		—			1,502
Corporate bonds and notes		77,477		79		(30	)		77,526
Subtotal		156,107		81		(30	)		156,158
Deferred compensation plan assets included in other assets		2,271		—		—			2,271
Total	$	158,378	$	81	$	(30	)	$	158,429

Investments consisted of the following as of December 31, 2013:

	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(Thousands of dollars)
Short-term investments:
Money Market Mutual Funds	$	18,470	$	—	$	—		$	18,470
Commercial Paper		2,999		—		—			2,999
Municipal bonds and notes		1,500		—		(1	)		1,499
Corporate bonds and notes		77,595		67		(29	)		77,633
Subtotal		100,564		67		(30	)		100,601
Deferred compensation plan assets included in other assets		2,109		—		—			2,109
Total	$	102,673	$	67	$	(30	)	$	102,710

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:

	March 31, 2014				December 31, 2013
	Amortized		Fair		Amortized		Fair
	Costs		Value		Costs		Value
	(Thousands of dollars)
Due in one year or less	$	37,811	$	37,849	$	32,536	$	32,538
Due within two years		41,166		41,179		49,558		49,593
Total	$	78,977	$	79,028	$	82,094	$	82,131

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:

	March 31, 2014				December 31, 2013
	Average		Average		Average		Average
	Coupon		Days To		Coupon		Days To
	Rate (%)		Maturity		Rate (%)		Maturity
Commercial Paper		—		—		0.150		86
Municipal bonds and notes		0.528		409		0.528		499
Corporate bonds and notes		2.032		638		2.134		390

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:

	March 31, 2014					December 31, 2013
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
	(Thousands of dollars)
Municipal bonds and notes	$	—	$	—		$	1,499	$	(1	)
Corporate bonds and notes		30,332		(30	)		34,772		(29	)
Total	$	30,332	$	(30	)	$	36,271	$	(30	)