Income Tax Expense - Tax Effects Of Temporary Differences That Give Rise To Significant Portions Of The Deferred Tax Assets And Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Deferred tax assets:
Inventories	$ 4,998	$ 4,800
Pension and other postretirement benefits	842	5,533
Timing differences related to revenue recognition	4,722	0
Lease liabilities	5,220	0
Net operating and capital loss carryforwards - domestic	563	602
Net operating loss carryforward - foreign	3,678	3,766
Other compensation-related costs and other cost accruals	8,953	7,764
State credit carryforward	2,366	1,914
Total deferred tax assets	31,342	24,379
Deferred tax liabilities:
Timing differences related to revenue recognition	0	(1,805)
ROU assets	5,220	0
Goodwill	(7,878)	(1,450)
Acquisition assets	(52,682)	(58,547)
Depreciation, software amortization	(21,283)	(18,288)
Net deferred tax liabilities before valuation allowance	55,721	55,711
Less valuation allowance	(1,932)	(4,504)
Net deferred tax liabilities	$ (57,653)	$ (60,215)