Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities
Net loss	$ (139,931)	$ (107,669)	$ (71,236)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	6,677	6,111	5,727
Non-cash lease expense	(1,043)
Loss on disposal of property and equipment		189	55
Stock-based compensation	17,096	11,170	2,961
Discount accretion on investment securities	(214)	(1,249)
Non-cash interest expense	152	233	254
Change in fair value of redeemable convertible preferred stock warrant liability			(13)
Amortization of debt discount	184	282	308
Changes in assets and liabilities:
Accounts receivable, net	(14,272)	(6,685)	(3,073)
Inventories	(4,956)	(1,302)	(4,202)
Prepaid expenses and other current assets	(3,683)	746	(1,760)
Other non-current assets	(554)	(2,064)	(812)
Accounts payable	(5,506)	3,278	3,759
Accrued expenses	(2,648)	4,210	(114)
Accrued Compensation	4,465	5,060	1,932
Other liabilities	1,978	(247)	50
Net cash used in operating activities	(142,255)	(87,937)	(66,164)
Cash flows from investing activities
Purchases of property and equipment	(9,868)	(14,757)	(3,688)
Proceeds from sale of property and equipment		21	17
Purchases of investments	(202,882)	(177,574)	(3,523)
Maturity of investments	98,100	87,500	34,500
Net cash provided by (used in) investing activities	(114,650)	(104,810)	27,306
Cash flows from financing activities
Proceeds from exercise of stock options	10,495	2,170	331
Proceeds from public offerings, net of underwriting discounts, commissions and offering expenses	295,563	156,208
Proceeds from issuance of Series D redeemable convertible preferred stock, net of issuance costs			90,850
Proceeds from issuance under employee stock purchase plan	3,428	2,700
Payments of deferred offering costs			(2,359)
Repayments of long-term debt	(3,333)	(2,500)
Repurchases of common stock for income tax withholding	(2,421)
Net cash provided by financing activities	303,732	158,578	88,822
Effect of exchange rates on cash, cash equivalents and restricted cash	21	30
Net increase (decrease) in cash, cash equivalents and restricted cash	46,848	(34,139)	49,964
Cash, cash equivalents, and restricted cash at beginning of year	47,398	81,537	31,573
Cash, cash equivalents, and restricted cash at end of year	94,246	47,398	81,537
Supplemental disclosure of cash flow information
Interest paid	438	779	751
Income taxes paid, net of refunds	172	291	179
Non-cash investing and financing activities
Property and equipment additions included in accrued expenses and accounts payable	1,333	170	344
Operating lease right-of-use assets obtained in exchange for operating lease liabilities	$ 3,718
Deferred offering costs included in accounts payable and accrued expenses			$ 1,308
Conversion of redeemable convertible preferred stock warrant liability to equity		631
Conversion of redeemable convertible preferred stock to common stock		$ 290,462