Fair Value of Financial Assets and Liabilities (Tables)

12 Months Ended

Sep. 30, 2019

Fair Value Disclosures [Abstract]

Financial Assets and Liabilities that were Subject to Fair Value Measurement on Recurring Basis

The following tables present information about the Company’s financial assets and liabilities that were subject to fair value measurement on a recurring basis as of September 30, 2019 and 2018 and indicate the fair value hierarchy of the valuation inputs utilized to determine such fair value:

	Fair Value Measurements at September 30, 2019 Using:
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Cash equivalents:
Money market funds	$	44,569	$	—	$	—	$	44,569
Marketable securities:
U.S. Treasury notes		170,515		—		—		170,515
Corporate bonds		—		111,837		—		111,837
Commercial paper		—		66,667		—		66,667
	$	215,084	$	178,504	$	—	$	393,588
Liabilities:
Series 1 nonconvertible preferred stock		—		—		1,628		1,628
	$	—	$	—	$	1,628	$	1,628

	Fair Value Measurements at September 30, 2018 Using:
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Cash equivalents:
Money market funds	$	51,025	$	—	$	—	$	51,025
Commercial paper		—		6,987		—		6,987
Corporate bonds		—		3,998		—		3,998
Marketable securities:
U.S. Treasury notes		42,703		—		—		42,703
Commercial paper		—		113,885		—		113,885
Corporate bonds		—		104,629		—		104,629
	$	93,728	$	229,499	$	—	$	323,227
Liabilities:
Series 1 nonconvertible preferred stock		—		—		1,628		1,628
	$	—	$	—	$	1,628	$	1,628

Fair Value Measurements of the Company's Warrant Liability and Series 1 Nonconvertible Preferred Stock

The recurring Level 3 fair value measurements of the Company’s warrant liability and Series 1 nonconvertible preferred stock using probability-weighted discounted cash flow include the following significant unobservable inputs:

	Range
	September 30,
Unobservable Input	2019	2018
Probabilities of payout	0%-60%	0%-70%
Discount rate	6.00%	6.25%

Rollforward of Aggregate Fair Values of Warrants and Outstanding Series 1 Nonconvertible Preferred Stock

The following table provides a rollforward of the aggregate fair values of the Company’s warrants for the purchase of Series 1 nonconvertible preferred stock and the outstanding Series 1 nonconvertible preferred stock for which fair value is determined by Level 3 inputs:

	Warrant Liability			Series 1 Nonconvertible Preferred Stock
	(in thousands)
Balance, September 30, 2016	$	1,251		$	159
Warrants exercised		(549	)		549
Increase in fair value		105			54
Balance, September 30, 2017		807			762
Warrants exercised		(766	)		766
Warrants expired		(41	)		—
Increase in fair value		—			100
Balance, September 30, 2018		—			1,628
Increase in fair value		—			—
Balance, September 30, 2019	$	—		$	1,628