MARKETABLE SECURITIES

The Company's marketable securities as of September 30, 2017 and December 31, 2016 were comprised of available-for-sale marketable securities which are carried at fair value, with the unrealized gains and losses reported in accumulated other comprehensive income. Realized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in other income or expense. Interest and dividends on securities classified as available-for-sale are included in interest income. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in interest income. During the nine months ended September 30, 2017, investment activity for the Company included $76.8 million in maturities, all relating to debt based marketable securities.

Marketable securities consisted of the following (in thousands):



	September 30, 2017		December 31, 2016
Marketable other than equity securities:
Commercial paper	$	5,497	$	30,303
Corporate debt securities	159,170		134,570
Securities of government sponsored entities	40,215		49,998
Total marketable securities:	$	204,882	$	214,871

The following is a summary of short-term marketable securities classified as available-for-sale as of September 30, 2017 (in thousands):



	Remaining Contractual Maturity (in years)	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Estimated Fair Value
Marketable other than equity securities:
Commercial paper	Less than 1	$	5,497	$	—	$	—		$	5,497
Corporate debt securities	Less than 1	92,029		—		(127		)	91,902
Securities of government-sponsored entities	Less than 1	36,821		10		(49		)	36,782
Total maturity less than 1 year		134,347		10		(176		)	134,181
Corporate debt securities	1 to 2	67,397		—		(129		)	67,268
Securities of government-sponsored entities	1 to 2	3,424		9		—			3,433
Total maturity 1 to 2 years		70,821		9		(129		)	70,701
Total available-for-sale securities		$	205,168	$	19	$	(305	)	$	204,882

The following is a summary of short-term marketable securities classified as available-for-sale as of December 31, 2016 (in thousands):



	Remaining Contractual Maturity (in years)	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Estimated Fair Value
Marketable Other than Equity Securities:
Commercial paper	Less than 1	$	30,330	$	—	$	(27	)	$	30,303
Corporate debt securities	Less than 1	64,794		7		(91		)	64,710
Securities of government-sponsored entities	Less than 1	19,500		—		(10		)	19,490
Total maturity less than 1 year		114,624		7		(128		)	114,503
Corporate debt securities	1 to 2	70,207		—		(347		)	69,860
Securities of government-sponsored entities	1 to 2	30,583		—		(75		)	30,508
Total maturity 1 to 2 years		100,790		—		(422		)	100,368
Total available-for-sale securities		$	215,414	$	7	$	(550	)	$	214,871

The primary objective of the Company’s investment portfolio is to enhance overall returns while preserving capital and liquidity. The Company’s investment policy limits interest-bearing security investments to certain types of instruments issued by institutions with primarily investment grade credit ratings and places restrictions on maturities and concentration by asset class and issuer.

The Company reviews the available-for-sale investments for other-than-temporary declines in fair value below cost basis each quarter and whenever events or changes in circumstances indicate that the cost basis of an asset may not be recoverable. This evaluation is based on a number of factors, including the length of time and the extent to which the fair value has been below the cost basis and adverse conditions related specifically to the security, including any changes to the credit rating of the security, and the intent to sell, or whether the Company will more likely than not be required to sell the security before recovery of its amortized cost basis. The assessment of whether a security is other-than-temporarily impaired could change in the future due to new developments or changes in assumptions related to any particular security. As of September 30, 2017 and December 31, 2016, the Company believed the cost basis for available-for-sale investments was recoverable in all material respects.