Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2018

Investments All Other Investments [Abstract]

Summary of 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

Summary of Contractual Maturities of Available-for-sale Securities

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