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. We determine cost, gains, and losses using the specific identification method.

Investments consisted of the following as of September 30, 2017:



	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(Thousands of dollars)
Investments:
Money market mutual funds	$	5,278	$	—	$	—		$	5,278
Commercial paper	9,423		—		(10		)	9,413
U.S. Government agencies	13,505		—		(14		)	13,491
Corporate bonds and notes	188,515		3		(283		)	188,235
Subtotal	216,721		3		(307		)	216,417
Deferred compensation plan assets included in other assets	2,630		—		—			2,630
Total	$	219,351	$	3	$	(307	)	$	219,047

Investments consisted of the following as of December 31, 2016:



	Cost Basis		Unrealized Gains		Unrealized Losses			Fair 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

At September 30, 2017 and December 31, 2016, we classified $12.4 million and $13.0 million respectively, of our aggregate investments as long-term investments and recorded them in our Condensed Consolidated Balance Sheets as Restricted cash and investments, as they are securing outstanding letters of credit with maturities beyond one year and a bond relating to foreign operations.

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



	September 30, 2017				December 31, 2016
	Amortized Costs		Fair Value		Amortized Costs		Fair Value
	(Thousands of dollars)
Due in one year or less	$	133,633	$	133,481	$	184,587	$	184,334
Due within two years	77,810		77,658		100,816		100,378
Total	$	211,443	$	211,139	$	285,403	$	284,712

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



	September 30, 2017		December 31, 2016
	Average Coupon Rate (%)	Average Days To Maturity	Average Coupon Rate (%)	Average Days To Maturity
Commercial paper	1.236	228	1.001	184
U.S. Government agencies	1.213	325	0.970	400
Corporate bonds and notes	1.715	295	1.745	318

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:



	September 30, 2017					December 31, 2016
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
	(Thousands of dollars)
Commercial paper	$	9,413	$	(10	)	$	27,867	$	(39	)
U.S. Government agencies	9,495		(10		)	13,263		(32		)
Corporate bonds and notes	102,767		(173		)	210,836		(602		)
Total	$	121,675	$	(193	)	$	251,966	$	(673	)

The following table presents the fair value and unrealized losses related to our investments that have been in a continuous unrealized loss position for more than twelve months as of:



	September 30, 2017					December 31, 2016
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
	(Thousands of dollars)
U.S. Government agencies	$	3,996	$	(4	)	$	—	$	—
Corporate bonds and notes	77,187		(110		)	24,196		(20		)
Total	$	81,183	$	(114	)	$	24,196	$	(20	)

From time to time over the periods covered in our financial statements included herein (and as illustrated in the foregoing tables), our investments have experienced net unrealized losses. We consider these declines in market value to be due to customary market fluctuations, 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 September 30, 2017 or December 31, 2016. We have also determined that we did not have any other than temporary impairments relating to credit losses on debt securities for the quarter ended September 30, 2017. For additional information regarding our criteria for making these assessments, see Note 2 to the financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2016.