NOTE 3. CASH, CASH EQUIVALENTS AND INVESTMENTS

Securities classified as cash, cash equivalents and short-term investments as of June 30, 2018 and December 31, 2017, are summarized below (in thousands). Estimated fair value is based on quoted market prices for these investments.


	June 30, 2018
			Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
Cash and cash equivalents:
Cash	$	2,932		—		—	$	2,932
Money market funds		67,611		—		—		67,611
Corporate bonds		2,664				—		2,664
Commercial paper		18,544		—		—		18,544
Total cash and cash equivalents	$	91,751	$	—	$	—	$	91,751
Short-term investments
U.S. treasury securities		8,459		1		—		8,460
Corporate bonds		38,788		—		(31)		38,757
Commercial paper		64,642		—		(2)		64,640
Asset-backed securities		9,126		—		(3)		9,123
Total short-term investments	$	121,015	$	1	$	(36)	$	120,980
Total cash equivalents and investments	$	212,766	$	1	$	(36)	$	212,731


	December 31, 2017
			Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
Cash and cash equivalents:
Cash	$	5,882	$	—	$	—	$	5,882
Money market funds		68,651		—		—		68,651
Commercial paper		850		—		—		850
Total cash equivalents and investments	$	75,383	$	—	$	—	$	75,383
Short-term investments
U.S. treasury securities	$	3,994		—		(1)	$	3,993
Corporate bonds		26,853		—		(26)		26,827
Commercial paper		19,584		—		(14)		19,570
Asset-backed securities		8,209		—		(6)		8,203
Total short-term investments	$	58,640	$	—	$	(47)	$	58,593
Total cash equivalents and investments	$	134,023	$	—	$	(47)	$	133,976

Cash equivalents consist of money market funds and other debt securities with original maturities of three months or less at the time of purchase, and the carrying amount is a reasonable approximation of fair value. The Company invests its cash in high quality securities of financial and commercial institutions. These securities are carried at fair value, which is based on readily available market information, with unrealized gains and losses included in “accumulated other comprehensive loss” within stockholders’ equity on the Company’s condensed consolidated balance sheets. The Company uses the specific identification method to determine the amount of realized gains or losses on sales of marketable securities. Realized gains or losses have been insignificant and are included in “other income, net” in the consolidated condensed statement of operations.

All available-for-sale securities held as of June 30, 2018, had contractual maturities of less than one year. The Company’s available-for-sale securities are subject to a periodic impairment review. The Company considers a debt security to be impaired when its fair value is less than its carrying cost, in which case the Company would further review the investment to determine whether it is other-than-temporarily impaired. When the Company evaluates an investment for other-than-temporary impairment, the Company reviews factors such as the length of time and extent to which fair value has been below cost basis, the financial condition of the issuer and any changes thereto, intent to sell, and whether it is more likely than not the Company will be required to sell the investment before the recovery of it cost basis. If an investment is other-than-temporarily impaired, the Company writes it down through the statement of operations to its fair value and establishes that value as a new cost basis for the investment. The Company did not identify any of its available-for-sale securities as other-than-temporarily impaired in any of the periods presented. As of June 30, 2018, no investment was in a continuous unrealized loss position for more than one year and the Company believes that is more likely than not the investments will be held until maturity or a forecasted recovery of fair value.