Cash equivalents and marketable securities

The Company considers all highly liquid investments with maturities of three months or less when purchased to be cash equivalents. Cash equivalents as of December 31, 2016 and December 31, 2015 consisted of money market funds.

Marketable securities as of December 31, 2016 consisted of corporate debt securities, commercial paper and U.S. government agency securities. Marketable securities as of December 31, 2015 consisted of corporate debt securities. Management determines the appropriate classification of the securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. The Company classifies its marketable securities as available-for-sale pursuant to ASC 320 Investments – Debt and Equity Securities. Marketable securities are recorded at fair value, with unrealized gains and losses included as a component of accumulated other comprehensive income (loss) in stockholders’ equity and a component of total comprehensive income (loss) in the consolidated statement of comprehensive income (loss), until realized. Realized gains and losses are included in investment income on a specific-identification basis. There were immaterial realized gains on marketable securities during the years ended December 31, 2016 and December 31, 2015.

The Company reviews marketable securities for other-than-temporary impairment whenever the fair value of a marketable security is less than the amortized cost and evidence indicates that a marketable security’s carrying amount is not recoverable within a reasonable period of time. Other-than-temporary impairments of investments are recognized in the consolidated statement of operations if the Company has experienced a credit loss, has the intent to sell the marketable security, or if it is more likely than not that the Company will be required to sell the marketable security before recovery of the amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, compliance with the Company’s investment policy, the severity and the duration of the impairment and changes in value subsequent to the end of the period.

Marketable securities at December 31, 2016 and December 31, 2015 consisted of the following:



	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
As of December 31, 2016
Current (due within 1 year):
Corporate debt securities	$	1,518,635	$	—	$	(395	)	$	1,518,240
Commercial paper	6,081,202		—		—			6,081,202
U.S. government agency securities	31,060,710		2,912		(4,131		)	31,059,491
Total	$	38,660,547	$	2,912	$	(4,526	)	$	38,658,933



	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
As of December 31, 2015
Current (due within 1 year):
Corporate debt securities	$	24,666,607	$	1,878	$	(16,137	)	$	24,652,348
Noncurrent (due after 1 year through 5 years):
Corporate debt securities	2,323,344				(10,395		)	2,312,949
Total	$	26,989,951	$	1,878	$	(26,532	)	$	26,965,297

The Company held six and eleven securities that were in an unrealized loss position at December 31, 2016 and December 31, 2015, respectively, all of which were in a continuous loss position for less than 12 months. The aggregate fair value of securities in an unrealized loss position was $16,519,620 and $24,967,915 at December 31, 2016 and December 31, 2015, respectively. There were no individual securities that were in a significant unrealized loss position as of December 31, 2016 or December 31, 2015. The Company evaluated its securities for other-than-temporary impairment and considered the decline in market value for the securities to be primarily attributable to current economic and market conditions. The Company has the intent and ability to hold such securities until recovery. Based on this analysis, these marketable securities were not considered to be other-than-temporarily impaired as of December 31, 2016.