Marketable Securities (Tables)

6 Months Ended

Mar. 31, 2018

The amortized cost and fair value of marketable securities as of March 31, 2018 and September 30, 2017 were as follows:



	March 31, 2018
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
	(in thousands)
Certificates of deposit	$	220	$	—	$	(1	)	$	219
Corporate notes/bonds	53,225		—		(575		)	52,650
U.S. government agency securities	2,408		—		(13		)	2,395
	$	55,853	$	—	$	(589	)	$	55,264



	September 30, 2017
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
	(in thousands)
Certificates of deposit	$	240	$	—	$	—		$	240
Corporate notes/bonds	47,811		2		(140		)	47,673
U.S. government agency securities	2,407		—		(5		)	2,402
	$	50,458	$	2	$	(145	)	$	50,315

Unrealized Gain (Loss) on Investments

The following tables summarize the fair value and gross unrealized losses aggregated by category and the length of time that individual securities have been in a continuous unrealized loss position as of March 31, 2018 and September 30, 2017.



	March 31, 2018
	Less than twelve months					Greater than twelve months					Total
	Fair Value		Gross unrealized loss			Fair Value		Gross unrealized loss			Fair Value		Gross unrealized loss
	(in thousands)
Certificates of deposit	$	219	$	(1	)	$	—	$	—		$	219	$	(1	)
Corporate notes/bonds	30,712		(413		)	21,938		(162		)	52,650		(575		)
U.S. government agency securities	—		—			2,395		(13		)	2,395		(13		)
	$	30,931	$	(414	)	$	24,333	$	(175	)	$	55,264	$	(589	)



	September 30, 2017
	Less than twelve months					Greater than twelve months					Total
	Fair Value		Gross unrealized loss			Fair Value		Gross unrealized loss			Fair Value		Gross unrealized loss
	(in thousands)
Certificates of deposit	$	240	$	—		$	—	$	—		$	240	$	—
Corporate notes/bonds	15,254		(43		)	28,885		(97		)	44,139		(140		)
U.S. government agency securities	—		—			2,402		(5		)	2,402		(5		)
	$	15,494	$	(43	)	$	31,287	$	(102	)	$	46,781	$	(145	)

Investments Classified by Contractual Maturity Date

The following table presents our available-for-sale marketable securities by contractual maturity date as of March 31, 2018 and September 30, 2017.



	March 31, 2018				September 30, 2017
	Amortized cost		Fair value		Amortized cost		Fair value
	(in thousands)				(in thousands)
Due in one year or less	$	22,772	$	22,636	$	18,274	$	18,244
Due after one year through three years	33,081		32,628		32,184		32,071
	$	55,853	$	55,264	$	50,458	$	50,315