Income Taxes - Schedule Of Deferred Tax Assets And Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 40,419	$ 65,383
Foreign tax credits	14,527	36,287
Capitalized research and development	23,274	27,546
Pension benefits	7,639	14,097
Prepaid expenses	15,886	12,540
Deferred revenue	2,146	2,274
Stock-based compensation	19,486	15,822
Other reserves not currently deductible	14,689	16,796
Amortization of intangible assets	130,825	147,385
Research and development and other tax credits	78,862	74,846
Lease liabilities	46,672	51,471
Fixed assets	78,249	53,025
Capital loss carryforward	3,955	35,156
Other	1,256	2,269
Gross deferred tax assets	477,885	554,897
Valuation allowance	(22,283)	(52,085)	$ (205,423)	$ (177,663)
Total deferred tax assets	455,602	502,812
Deferred tax liabilities:
Acquired intangible assets not deductible	(118,360)	(108,746)
Lease assets	(36,940)	(37,273)
Pension prepayments	(2,622)	(2,834)
Deferred revenue	(35,193)	(2,662)
Depreciation	(6,937)	(7,121)
Unbilled accounts receivable	0	(6,391)
Deferred income	(5,991)	(21,744)
Prepaid commissions	(13,356)	(16,990)
Other	(8,508)	(5,427)
Total deferred tax liabilities	(227,907)	(209,188)
Net deferred tax assets	$ 227,695	$ 293,624