2. INVESTMENTS

We classify all of our short-term investments as available-for-sale. We carry these at fair value and report unrealized gains and losses, net of taxes, in Accumulated other comprehensive loss, which is a separate component of shareholders’ equity in our Condensed Consolidated Balance Sheets. These unrealized gains and losses are also reflected in our Condensed Consolidated Statements of Comprehensive Income and Condensed Consolidated Statements of Shareholders’ Equity. Cost, gains, and losses are determined using the specific identification method.

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

$14.7 million of our investments at March 31, 2014 and December 31, 2013 are long-term and included in our Condensed Consolidated Balance Sheets as Restricted investments, as they are securing outstanding letters of credit with maturities beyond one year.

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

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

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	)

As of March 31, 2014 and December 31, 2013, we had no investments in a continuous unrealized loss position for more than twelve months.

From time to time over the periods covered in our financial statements included herein, our investments have experienced net unrealized losses. We consider these declines in market value to be due to market conditions, and we do not plan to sell these investments prior to maturity. For these reasons, we do not consider any of our investments to be other than temporarily impaired at March 31, 2014 or December 31, 2013. The assessment of whether an investment in a debt security has suffered an other-than-temporary impairment is based on whether we intend to sell, or it is more likely than not we will be required to sell, the debt security before recovery of its amortized costs. Further, if we do not expect to recover the entire amortized cost basis of the debt security, an other-than-temporary impairment is considered to have occurred and it is measured by the present value of cash flows expected to be collected less the amortized cost basis (credit loss). We have determined that we did not have any other-than-temporary impairments relating to credit losses on debt securities for the three months ended March 31, 2014.