Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Valuation allowance - deferred tax assets
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period		$ 3,810	$ 3,291	$ 5,952
Charged to costs and expenses		670	529	521
Charged to Other Accounts		0	0	0
Deductions		108	10	3,182
Balance at end of period		4,372	3,810	3,291
Valuation account - doubtful accounts
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period		968	785	341
Charged to costs and expenses		2,534	635	729
Charged to Other Accounts		0	0	40	[1]
Deductions	[2]	(276)	452	325
Balance at end of period		3,778	968	785
Reserve for future credit returns and pricing adjustments
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period		2,677	2,560	2,169
Charged to costs and expenses		17,816	12,640	10,715
Charged to Other Accounts		0	0	0
Deductions		19,017	12,523	10,324
Balance at end of period		$ 1,476	$ 2,677	$ 2,560

[1] Established through purchase accounting relating to the acquisition of TempAlert

[2] Uncollectible accounts charged against allowance, net of recoveries