INVESTMENTS (Tables)

6 Months Ended

Jun. 30, 2014

Investments Debt And Equity Securities [Abstract]

Components of Investments

Investments consisted of the following as of June 30, 2014:

	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(Thousands of dollars)
Investments:
Money market mutual funds	$	69,048	$	—	$	—		$	69,048
Municipal bonds and notes		1,500		4		—			1,504
Corporate bonds and notes		80,657		97		(25	)		80,729
Subtotal		151,205		101		(25	)		151,281
Deferred compensation plan assets included in other assets		2,359		—		—			2,359
Total	$	153,564	$	101	$	(25	)	$	153,640

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

	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(Thousands of dollars)
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:

	June 30, 2014				December 31, 2013
	Amortized Costs		Fair Value		Amortized Costs		Fair Value
	(Thousands of dollars)
Due in one year or less	$	43,073	$	43,129	$	32,536	$	32,538
Due within two years		39,084		39,104		49,558		49,593
Total	$	82,157	$	82,233	$	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:

	June 30, 2014				December 31, 2013
	Average Coupon Rate (%)		Average Days To Maturity		Average Coupon Rate (%)		Average Days To Maturity
Commercial paper		—		—		0.150		86
Municipal bonds and notes		0.528		318		0.528		499
Corporate bonds and notes		1.705		366		2.134		390