Financial Instruments

9 Months Ended

Sep. 30, 2018

Investments All Other Investments [Abstract]

Financial Instruments

4. Financial Instruments

The following is a summary of financial instruments (in thousands):

	As of September 30, 2018
			Gross		Gross
			Unrealized		Unrealized			Estimated Fair
	Cost		Gains		Losses			Values
Available-for sale securities
Commercial Paper	$	9,883	$	—	$	(8	)	$	9,875
Money market funds		4,911		—		—			4,911
Corporate bonds		49,242		—		(112	)		49,130
U.S. government securities		1,500		—		—			1,500
Total available-for-sale securities	$	65,536	$	—	$	(120	)	$	65,416
Reported in:
Cash and cash equivalents								$	6,909
Short-term investments									58,507
Total available-for-sale securities								$	65,416

	As of December 31, 2017
			Gross		Gross
			Unrealized		Unrealized			Estimated Fair
	Cost		Gains		Losses			Values
Available-for sale securities
Commercial paper	$	13,927	$	—	$	(11	)	$	13,916
Money market funds		1,269		—		—			1,269
Corporate bonds		36,534		—		(81	)		36,453
U.S. government securities		2,489		—		(4	)		2,485
Total available-for-sale securities	$	54,219	$	—	$	(96	)	$	54,123
Reported in:
Cash and cash equivalents								$	5,761
Short-term investments									48,362
Total available-for-sale securities								$	54,123

The contractual maturities of available-for-sale securities are presented in the following table (in thousands):

	As of September 30, 2018
	Amortized Cost Basis		Estimated Fair Value
Due in one year or less	$	59,517	$	59,408
Due between one and five years		6,019		6,008
	$	65,536	$	65,416

Gross realized gains and gross realized losses on sales of available-for-sale securities for the three and nine months ended September 30, 2018 were not significant.As of September 30, 2018 and December 31, 2017, there were no individual securities that had been in a continuous loss position for 12 months or longer.