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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, 2016, 2015, and 2014, we received proceeds from the sales of these securities of $316.5 million, $506.0 million, and $363.1 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, 2016:


			Unrealized		Unrealized			Fair
	Cost Basis		Gains		Losses			Value
	(Thousands of dollars)
Investments:
Money market mutual funds	$	18,118	$	—	$	—		$	18,118
Commercial paper		27,906		—		(39	)		27,867
U.S. government agencies		13,295		—		(32	)		13,263
Corporate bonds and notes		244,202		2		(622	)		243,582

Subtotal		303,521		2		(693	)		302,830

Deferred compensation plan assets included in other assets		2,394		—		—			2,394

Total	$	305,915	$	2	$	(693	)	$	305,224

$13.0 million of our investments at December 31, 2016 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, 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.

The following table presents the cost and fair value of our debt investments based on maturities as of December 31,


	2016				2015
	Amortized		Fair		Amortized		Fair
	Costs		Value		Costs		Value
	(Thousands of dollars)
Due in one year or less	$	184,587	$	184,334	$	152,444	$	152,212
Due within two years		100,816		100,378		130,110		129,466

Total	$	285,403	$	284,712	$	282,554	$	281,678

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


	2016				2015
	Average		Average		Average		Average
	Coupon		Days To		Coupon		Days To
	Rate (%)		Maturity		Rate (%)		Maturity
Commercial paper		1.001		184		0.553		154
U.S. government agencies		0.970		400		0.865		599
Corporate bonds and notes		1.745		318		1.757		331

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,


	2016					2015
			Unrealized					Unrealized
	Fair Value		Losses			Fair Value		Losses
	(Thousands of dollars)
Commercial paper	$	27,867	$	(39	)	$	5,981	$	(5	)
U.S. government agencies		13,263		(32	)		8,969		(30	)
Corporate bonds and notes		210,836		(602	)		232,347		(793	)

Total	$	251,966	$	(673	)	$	247,297	$	(828	)

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,


	2016					2015
			Unrealized					Unrealized
	Fair Value		Losses			Fair Value		Losses
	(Thousands of dollars)
Corporate bonds and notes	$	24,196	$	(20	)	$	28,866	$	(48	)

Total	$	24,196	$	(20	)	$	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, 2016 and 2015. 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, 2016 or 2015.