Supplementary Balance Sheet Information (Tables)

12 Months Ended

Sep. 30, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Summary of Accounts Receivable

The following is a summary of accounts receivable at September 30, 2020 and 2019 (in thousands):

	September 30,
	2020		2019
Accounts receivable	$	195,587	$	169,317
Less allowance for doubtful accounts		(7,216)		(3,644)
Less allowance for sales returns		(80)		(71)
Accounts receivable, net	$	188,291	$	165,602

Allowance for Doubtful Accounts Activity

The allowance for doubtful accounts activity for the fiscal years ended September 30, 2020, 2019 and 2018 is as follows (in thousands):

	Balance at				Reversals of		Write-		Balance at
	Beginning of				Bad Debt		offs and		End of
Description	Period		Provisions		Expense		Adjustments		Period
2020 Allowance for doubtful accounts	$	3,644	$	4,587	$	(1,018)	$	3	$	7,216
2019 Allowance for doubtful accounts		1,113		3,405		(693)		(181)		3,644
2018 Allowance for doubtful accounts		1,381		708		(724)		(252)		1,113

The allowance for sales returns activity for the fiscal years ended September 30, 2020, 2019 and 2018 is as follows (in thousands):

	Balance at				Write-		Balance at
	Beginning of				offs and		End of
Description	Period		Provisions		Adjustments		Period
2020 Allowance for sales returns	$	71	$	9	$	—	$	80
2019 Allowance for sales returns		45		26		—		71
2018 Allowance for sales returns		81		(36)		—		45

Summary of Inventories

The following is a summary of inventories at September 30, 2020 and 2019 (in thousands):

	September 30,
	2020		2019
Inventories
Raw materials and purchased parts	$	73,609	$	67,176
Work-in-process		16,461		13,684
Finished goods		24,764		18,585
Total inventories	$	114,834	$	99,445

The activity for excess and obsolete inventory reserves is as follows for the fiscal years ended September 30, 2020, 2019 and 2018 (in thousands):

	Balance at				Inventory		Balance at
	Beginning of				Disposals and		End of
Description	Period			Provisions	Adjustments		Period
2020 Reserves for excess and obsolete inventory	$	16,298	$	5,152	$	(4,334)	$	17,116
2019 Reserves for excess and obsolete inventory		14,953		5,865		(4,520)		16,298
2018 Reserves for excess and obsolete inventory		17,734		4,455		(7,236)		14,953

Valuation Allowance for Deferred Tax Assets Activity

The activity for valuation allowance for deferred tax assets is as follows for the fiscal years ended September 30, 2020, 2019 and 2018 (in thousands):

	Balance at						Balance at
	Beginning of		Charged to		Charged to		End of
Description	Period		Provisions		Other Accounts		Period
2020 Valuation allowance for deferred tax assets	$	16,093	$	(1,526)	$	(968)	$	13,599
2019 Valuation allowance for deferred tax assets		18,581		(3,475)		987		16,093
2018 Valuation allowance for deferred tax assets		92,297		(72,842)		(874)		18,581

Product Warranty and Retrofit Activity on Gross Basis

	Amount
Balance at September 30, 2017	$	5,479
Accruals for warranties during the year		5,209
Costs incurred during the year		(4,348)
Balance at September 30, 2018		6,340
Accruals for warranties during the year		8,688
Costs incurred during the year		(7,853)
Balance at September 30, 2019		7,175
Accruals for warranties during the year		8,430
Costs incurred during the year		(7,404)
Balance at September 30, 2020	$	8,201