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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 (income), which is a separate component of shareholders’ equity in our consolidated balance sheets, and in our consolidated statements of shareholders’ equity. Cost, gains, and losses are determined using the specific identification method. In the years ended December 31, 2015, 2014, and 2013, we received proceeds from the sales of these securities of $506.0 million, $363.1 million, and $339.0 million, respectively. Gains and losses on these sales were negligible and all amounts reclassified from accumulated other comprehensive income were immaterial.

Investments consisted of the following as of December 31, 2015:


			Unrealized		Unrealized			Fair
	Cost Basis		Gains		Losses			Value
	(Thousands of dollars)
Investments:
Money market mutual funds	$	18,181	$	—	$	—		$	18,181
Commercial paper		5,986		—		(5	)		5,981
U.S. government agencies		11,499		—		(30	)		11,469
Corporate bonds and notes		265,069		—		(841	)		264,228

Subtotal		300,735		—		(876	)		299,859

Deferred compensation plan assets included in other assets		2,294		—		—			2,294

Total	$	303,029	$	—	$	(876	)	$	302,153

$15.3 million of our investments at December 31, 2015 were long-term and included on the balance sheet as Restricted investments as they are securing outstanding letters of credit with maturities beyond one year.

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


			Unrealized		Unrealized			Fair
	Cost Basis		Gains		Losses			Value
	(Thousands of dollars)
Investments:
Money market mutual funds	$	68,612	$	—	$	—		$	68,612
Municipal bonds and notes		1,500		2		—			1,502
Corporate bonds and notes		130,864		19		(268	)		130,615

Subtotal		200,976		21		(268	)		200,729

Deferred compensation plan assets included in other assets		2,386		—		—			2,386

Total	$	203,362	$	21	$	(268	)	$	203,115

$15.5 million of our investments at December 31, 2014 were long-term and included on the balance sheet 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 December 31,


	2015				2014
	Amortized		Fair		Amortized		Fair
	Costs		Value		Costs		Value
	(Thousands of dollars)
Due in one year or less	$	152,444	$	152,212	$	70,180	$	70,169
Due within two years		130,110		129,466		62,184		61,948

Total	$	282,554	$	281,678	$	132,364	$	132,117

The following table presents the average coupon rate percentage and the average days to maturity of our debt investments as of December 31,

2015

2014

Average

Coupon

Days To

Coupon

Days To

Rate (%)

Maturity

Rate (%)

Maturity

Commercial paper

0.553

154

n/a

U.S. government agencies

0.865

599

n/a

Municipal bonds and notes

n/a

0.528

134

Corporate bonds and notes

1.757

331

1.828

348

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 December 31,


	2015					2014
			Unrealized					Unrealized
	Fair Value		Losses			Fair Value		Losses
	(Thousands of dollars)
Commercial paper	$	5,981	$	(5	)	$	—	$	—
U.S. government agencies		8,969		(30	)		—		—
Corporate bonds and notes		232,347		(793	)		100,071		(268	)

Total	$	247,297	$	(828	)	$	100,071	$	(268	)

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 December 31,


	2015					2014
			Unrealized					Unrealized
	Fair Value		Losses			Fair Value		Losses
	(Thousands of dollars)
Corporate bonds and notes	$	28,866	$	(48	)	$	—	$	—

Total	$	28,866	$	(48	)	$	—	$	—

As noted above, 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 December 31, 2015 and 2014. The assessment of whether an investment in a debt security has suffered an other-than-temporary impairment is based on whether the Company has the intent to sell or more likely than not will be required to sell the debt security before recovery of its amortized costs. Further, if the Company does 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). The Company determined it did not have any other-than-temporary impairments relating to credit losses on debt securities for the year ended December 31, 2015 or 2014.