Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Revenue:
Total revenue	$ 34,995	$ 22,822	$ 57,292	$ 45,438
Operating costs and expenses:
Type of Cost, Good or Service [Extensible List]	Product Sales [Member]	Product Sales [Member]	Product Sales [Member]	Product Sales [Member]
Product costs	$ 4,170	$ 3,769	$ 7,913	$ 6,972
Research and development	12,875	11,935	23,757	24,077
Selling, general and administrative	7,907	6,733	14,930	13,676
Acquired intangible asset amortization	560	541	1,116	1,135
Total operating costs and expenses	25,512	22,978	47,716	45,860
Operating income (loss)	9,483	(156)	9,576	(422)
Other income (expense):
Investment income, net	28	210	69	460
Interest expense	(59)	(30)	(119)	(70)
Foreign exchange gain (loss)	73	(30)	(107)	(77)
Impairment loss on strategic investment and other		(479)		(478)
Other income (expense)	42	(329)	(157)	(165)
Income (loss) before income taxes	9,525	(485)	9,419	(587)
Income tax (provision) benefit	(1,438)	1,947	(1,606)	2,197
Net income	$ 8,087	$ 1,462	$ 7,813	$ 1,610
Basic net income per share	$ 0.59	$ 0.11	$ 0.57	$ 0.12
Diluted net income per share	$ 0.58	$ 0.11	$ 0.56	$ 0.12
Weighted average number of shares outstanding:
Basic	13,746	13,507	13,699	13,474
Diluted	13,981	13,751	13,915	13,779
Product Sales [Member]
Revenue:
Total revenue	$ 11,783	$ 11,770	$ 21,885	$ 21,744
Royalties and License Fees [Member]
Revenue:
Total revenue	20,052	8,221	29,386	18,369
Research, Development and Other [Member]
Revenue:
Total revenue	$ 3,160	$ 2,831	$ 6,021	$ 5,325