Available-for-sale Securities and Fair Value on Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Summary of Available-for-Sale Securities

The following is a summary of available-for-sale securities at March 31, 2019 (in thousands):

	March 31, 2019
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Money market funds	$	4,145	$	—	$	—		$	4,145
United States government agency securities		7,488		—		(11	)		7,477
Corporate debt securities		64,008		18		(77	)		63,949
Total available-for-sale securities	$	75,641	$	18	$	(88	)	$	75,571

The following is a summary of available-for-sale securities at December 31, 2018 (in thousands):

	December 31, 2018
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Money market funds	$	6,167	$	—	$	—		$	6,167
United States government agency securities		15,971		—		(23	)		15,948
Corporate debt securities		73,028		2		(260	)		72,770
Total available-for-sale securities	$	95,166	$	2	$	(283	)	$	94,885

Available-for-Sale Debt Securities by Original Contractual Maturity

Available-for-sale securities at March 31, 2019 and December 31, 2018, consisted of the following by contractual maturity (in thousands):

	March 31, 2019				December 31, 2018
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
One year or less	$	75,641	$	75,571	$	85,227	$	84,957
Greater than one year and less than five years		—		—		9,939		9,928
Total available-for-sale securities	$	75,641	$	75,571	$	95,166	$	94,885

Available-for-Sale Marketable Securities in Unrealized Position

The following tables show all available-for-sale marketable securities in an unrealized loss position for which an other-than-temporary impairment has not been recognized and the related gross unrealized losses and fair value, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position (in thousands):

	March 31, 2019
	Less than 12 Months					12 Months or Greater					Total
	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss			Fair Value		Unrealized Loss
United States government agency    securities	$	—	$	—		$	7,477	$	(11	)	$	7,477	$	(11	)
Corporate debt securities		—		—			47,479		(77	)		47,479		(77	)
Total available-for-sale securities	$	—	$	—		$	54,956	$	(88	)	$	54,956	$	(88	)
	December 31, 2018
	Less than 12 Months					12 Months or Greater					Total
	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss			Fair Value		Unrealized Loss
United States government agency    securities	$	14,948	$	(22	)	$	999	$	(1	)	$	15,947	$	(23	)
Corporate debt securities		60,813		(231	)		9,976		(29	)		70,789		(260	)
Total available-for-sale securities	$	75,761	$	(253	)	$	10,975	$	(30	)	$	86,736	$	(283	)

Fair Values of Financial Assets and Liabilities

The fair values of the Company’s financial assets and liabilities were determined using the following inputs at March 31, 2019 (in thousands):

	Balance sheet			Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
	classification	Total		(Level 1)		(Level 2)		(Level 3)
Money market funds	Cash and cash equivalents	$	4,145	$	4,145	$	—	$	—
United States government agency securities	Short-term investments		7,477		—		7,477		—
Corporate debt securities	Short-term investments		63,949		—		63,949		—
Total financial assets		$	75,571	$	4,145	$	71,426	$	—

The fair values of the Company’s financial assets and liabilities were determined using the following inputs at December 31, 2018 (in thousands):

	Balance sheet			Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
	classification	Total		(Level 1)		(Level 2)		(Level 3)
Money market funds	Cash and cash equivalents	$	6,167	$	6,167	$	—	$	—
United States government agency securities	Short-term investments		15,948		—		15,948		—
Corporate debt securities	Short-term investments		72,770		—		72,770		—
Total financial assets		$	94,885	$	6,167	$	88,718	$	—