Summary of Significant Accounting Policies (Tables)

12 Months Ended

Sep. 30, 2021

Accounting Policies [Abstract]

Allowance for Doubtful Accounts

Our allowance for credit losses changed during the fiscal year ended September 30, 2021 and 2020 as follows:

	2021		2020
Beginning Balance	$	583	$	2,377
Amount of charge (benefit) to expense	76		(1,122)
Deductions and adjustments	(132)		(672)
Ending Balance at September 30	$	527	$	583

Customers Who Represent more than 10% of Revenue

Customers who represented more than 10% of consolidated revenue, all of which are in the Electronic Materials segment, are as follows:

	Year Ended September 30,
	2021		2020		2019
Intel	13	%	15	%	14	%
Samsung Group	11	%	11	%	11	%

Of those customers who represented more than 10% of consolidated revenue, their net accounts receivable as a percentage of total net accounts receivable are as follows:

	September 30,
	2021		2020
Intel	9	%	9	%
Samsung Group	7	%	7	%

Schedule of Property, Plant and Equipment

Property, plant and equipment are recorded at cost. Depreciation is based on the following estimated useful lives of the assets using the straight-line method:

Land improvements	10-20 years
Buildings	15-30 years
Machinery and equipment	3-20 years
Furniture and fixtures	5-10 years
Vehicles	5-8 years
Information systems	3-5 years
Assets under financing leases	The shorter of the term of the lease or estimated useful life