Investments

Short-term investments consist of investments with maturities greater than ninety days and less than one year from the balance sheet date. Long-term investments consist of investments with maturities of greater than one year that are not expected to be used to fund current operations. The Company classifies all of its investments as available-for-sale securities. Accordingly, these investments are recorded at fair value. Realized gains and losses, amortization and accretion of discounts and premiums are included in other income, net. Unrealized gains and losses on available-for-sale securities are included in other comprehensive income as a component of stockholders’ equity until realized.

Cash equivalents, short-term investments and long-term investments as of December 31, 2018 were comprised as follows (in thousands):



	December 31, 2018
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents and short-term investments:
Money market funds, included in cash equivalents	$	41,434	$	—	$	—		$	41,434
Corporate debt securities	65,887		2		(39		)	65,850
U.S. Treasuries	53,765		1		(8		)	53,758
Government agency securities	28,866		—		(34		)	28,832
Total cash equivalents and short-term investments	189,952		3		(81		)	189,874
Long-term investments:
Corporate debt securities	2,001		—		(8		)	1,993
Government agency securities	3,989		8		—			3,997
Total long-term investments	5,990		8		(8		)	5,990
Total cash equivalents and investments	$	195,942	$	11	$	(89	)	$	195,864

Cash equivalents, short-term investments and long-term investments as of December 31, 2017 were comprised as follows (in thousands):



	December 31, 2017
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents and short-term investments:
Money market funds, included in cash equivalents	$	21,059	$	—	$	—		$	21,059
Corporate debt securities	58,136		—		(64		)	58,072
U.S. Treasuries	111,049		—		(101		)	110,948
Government agency securities	43,204		—		(131		)	43,073
Total cash equivalents and short-term investments	233,448		—		(296		)	233,152
Long-term investments:
Corporate debt securities	7,117		—		(16		)	7,101
Government agency securities	15,195		—		(97		)	15,098
Total long-term investments	22,312		—		(113		)	22,199
Total cash equivalents and investments	$	255,760	$	—	$	(409	)	$	255,351

As of December 31, 2018 and 2017, the aggregate fair value of securities that were in an unrealized loss position for less than twelve months was $81.4 million and $113.9 million, respectively. As of December 31, 2018 and 2017, the aggregate fair value of securities that were in an unrealized loss position for more than twelve months was $22.3 million and $107.9 million, respectively. As of December 31, 2018, the Company did not intend to sell, and would not be more likely than not required to sell, the securities in an unrealized loss position before recovery of their amortized cost bases. Furthermore, the Company determined that there was no material change in the credit risk of these securities. As a result, the Company determined it did not hold any securities with any other-than-temporary impairment as of December 31, 2018.

There were immaterial realized gains and losses on available-for-sale securities during the years ended December 31, 2018 and 2017.