Investments

We classified all of our investments as "available for sale" as of April 1, 2017 and December 31, 2016. Accordingly, we state our investments at estimated fair value. Fair values are determined based on quoted market prices or pricing models using current market rates. We deem all investments to be available to meet current working capital requirements. The cost of securities sold was determined based on the specific identification method.

The following table summarizes our investments:



	April 1, 2017								December 31, 2016
	Amortized Cost		Accumulated Other Comprehensive Income				Estimated Fair Value		Amortized Cost		Accumulated Other Comprehensive Income				Estimated Fair Value
Available-for-sale securities (in thousands)	Amortized Cost		Gains		Losses		Estimated Fair Value		Amortized Cost		Gains		Losses		Estimated Fair Value
Commercial paper	$	31,702	$	2	$	25	$	31,679	$	23,744	$	—	$	60	$	23,684
Money market funds	2,189		—		—		2,189		2,266		—		—		2,266
U.S. treasury bills and notes	10,485		—		8		10,477		29,467		1		7		29,461
Securities and obligations of U.S. government agencies	134,487		11		317		134,181		127,961		8		265		127,704
Total	$	178,863	$	13	$	350	$	178,526	$	183,438	$	9	$	332	$	183,115

The following table identifies the balance sheet classifications of our investments:



(In thousands)	April 1, 2017		December 31, 2016
Cash equivalents	$	24,129	$	2,266
Short-term investments	154,397		180,849
Investments, at estimated fair value	$	178,526	$	183,115

The gross amortized cost and estimated fair value of our investments at April 1, 2017 and December 31, 2016, by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because the issuers of the securities may have the right to prepay obligations without prepayment penalties.



	April 1, 2017				December 31, 2016
(In thousands)	Gross Amortized Cost		Fair Value		Gross Amortized Cost		Fair Value
Due in one year or less	$	122,738	$	122,577	$	112,164	$	112,058
Due after one year through five years	56,125		55,949		71,274		71,057
Total	$	178,863	$	178,526	$	183,438	$	183,115

The following table provides the breakdown of the cash equivalents and investments with unrealized losses at April 1, 2017:



	In Loss Position for Less Than 12 Months				Total
(In thousands)	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Commercial papers	14,272		25		14,272		25
U.S. treasury bills and notes	$	10,477	$	8	$	10,477	$	8
Securities and obligations of U.S. government agencies	119,679		317		119,679		317
Total	$	144,428	$	350	$	144,428	$	350

The following table provides the breakdown of the cash equivalents and investments with unrealized losses at December 31, 2016:



	In Loss Position for Less Than 12 Months				Total
(In thousands)	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Commercial papers	$	17,693	$	60	$	17,693	$	60
U.S. treasury bills and notes	$	18,463	$	7	$	18,463	$	7
Securities and obligations of U.S. government agencies	$	103,426	$	265	$	103,426	$	265
Total	$	139,582	$	332	$	139,582	$	332

We review our investment portfolio regularly for impairment. A security is considered impaired when its fair value is less than its cost basis. If we intend to sell an impaired debt security or it is more likely than not that we will be required to sell it prior to recovery of its amortized cost basis, and other-than-temporary-impairment (“OTTI”) is deemed to have occurred. In these instances, the OTTI loss is recognized in earnings equal to the entire difference between the debt security’s amortized cost basis and its fair value at the balance sheet date.

If we do not intend to sell an impaired debt security and it is not more likely than not that we will be required to sell the security prior to recovery of its amortized cost basis, we must determine whether the security will recover its amortized cost basis. If we conclude that we will not recover the security’s amortized cost basis, a credit loss exists and the resulting OTTI is separated into:


•	The amount representing the credit loss, which is recognized in earnings, and


•	The amount related to all other factors, which is recognized in other comprehensive income.

As part of this assessment, we will consider the various characteristics of each security, including, but not limited to the following: the length of time and the extent to which the fair value has been less than the amortized cost basis; adverse conditions specifically related to the security, an industry, or a geographic area; the payment structure of the debt security; failure of the issuer of the security to make scheduled interest or principal payments; any changes to the rating of the security by a rating agency and related outlook or status; and recoveries or additional declines in fair value subsequent to the balance sheet date. The relative importance of this information varies based on the facts and circumstances surrounding each security, as well as the economic environment at the time of assessment.

We have not recorded any OTTI on our investments for the three month period ended April 1, 2017 or for the corresponding period of 2016.