CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning Balance (in shares) at Sep. 30, 2020		41,780,000
Beginning Balance at Sep. 30, 2020	$ 132,243	$ 42	$ 146,518		$ (13,994)	$ (323)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		260,000
Exercise of stock options	1,958		1,958
Settlement of restricted stock units (in shares)		935,000
Settlement of restricted stock units		$ 1	(1)
Issuance of common stock under employee stock purchase plan (in shares)		77,000
Issuance of common stock under employee stock purchase plan	792		792
Stock-based compensation expense	5,715		5,715
Sale of convertible senior notes warrants	23,909		23,909
Components of other comprehensive loss:
Net income	3,186				3,186
Currency translation adjustment	112					112
Change in unrealized gain (loss) on investments	(186)					(186)
Other comprehensive income (loss)	3,112
Ending Balance (in shares) at Mar. 31, 2021		43,052,000
Ending Balance at Mar. 31, 2021	167,729	$ 43	178,891		(10,808)	(397)
Beginning Balance (in shares) at Dec. 31, 2020		42,668,000
Beginning Balance at Dec. 31, 2020	141,753	$ 43	151,153		(11,827)	2,384
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		18,000
Exercise of stock options	69		69
Settlement of restricted stock units (in shares)		289,000
Settlement of restricted stock units	(1)		(1)
Issuance of common stock under employee stock purchase plan (in shares)		77,000
Issuance of common stock under employee stock purchase plan	793		793
Stock-based compensation expense	2,968		2,968
Sale of convertible senior notes warrants	23,909		23,909
Components of other comprehensive loss:
Net income	1,019				1,019
Currency translation adjustment	(2,648)					(2,648)
Change in unrealized gain (loss) on investments	(133)					(133)
Other comprehensive income (loss)	(1,762)
Ending Balance (in shares) at Mar. 31, 2021		43,052,000
Ending Balance at Mar. 31, 2021	$ 167,729	$ 43	178,891		(10,808)	(397)
Beginning Balance (in shares) at Sep. 30, 2021	44,168,745	44,169,000		(8,000)
Beginning Balance at Sep. 30, 2021	$ 192,830	$ 44	199,935	$ (140)	(6,066)	(943)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	25,625	25,000
Exercise of stock options	$ 206		206
Settlement of restricted stock units (in shares)		973,000
Settlement of restricted stock units		$ 1	(1)
Issuance of common stock under employee stock purchase plan (in shares)		71,000
Issuance of common stock under employee stock purchase plan	923		923
Stock-based compensation expense	6,429		6,429
Repurchases and retirement of common stock (in shares)		(894,000)		8,000
Repurchases and retirement of common stock	(14,828)	$ (1)	(1)	$ 140	(14,966)
Components of other comprehensive loss:
Net income	5,035				5,035
Currency translation adjustment	(3,129)					(3,129)
Change in unrealized gain (loss) on investments	(1,098)					(1,098)
Other comprehensive income (loss)	$ 808
Ending Balance (in shares) at Mar. 31, 2022	44,344,361	44,344,000		0
Ending Balance at Mar. 31, 2022	$ 186,368	$ 44	207,491	$ 0	(15,997)	(5,170)
Beginning Balance (in shares) at Dec. 31, 2021		44,297,000
Beginning Balance at Dec. 31, 2021	187,429	$ 44	203,091		(13,226)	(2,480)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		16,000
Exercise of stock options	179		179
Settlement of restricted stock units (in shares)		248,000
Issuance of common stock under employee stock purchase plan (in shares)		71,000
Issuance of common stock under employee stock purchase plan	923		923
Stock-based compensation expense	3,298		3,298
Repurchases and retirement of common stock (in shares)		(288,000)
Repurchases and retirement of common stock	(4,682)				(4,682)
Components of other comprehensive loss:
Net income	1,911				1,911
Currency translation adjustment	(1,862)					(1,862)
Change in unrealized gain (loss) on investments	(828)					(828)
Other comprehensive income (loss)	$ (779)
Ending Balance (in shares) at Mar. 31, 2022	44,344,361	44,344,000		0
Ending Balance at Mar. 31, 2022	$ 186,368	$ 44	$ 207,491	$ 0	$ (15,997)	$ (5,170)