Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Sep. 30, 2021
Assets:
Available-for-sale securities	$ 1,076,732	$ 3,679
Fair Value, Measurements, Recurring
Assets:
Available-for-sale securities	1,076,732	3,679
Foreign exchange contracts	130	153
Net Investment Hedge	10,673
Total Assets	1,851,896	3,853
Liabilities:
Foreign exchange contracts	734	165
Acquisition-related contingent consideration		9,400
Total Liabilities	734	9,565
Fair Value, Measurements, Recurring | Cash equivalents
Assets:
Cash equivalents	764,361	21
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Recurring
Assets:
Available-for-sale securities	517,457
Total Assets	1,281,818	21
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Cash equivalents
Assets:
Cash equivalents	764,361	21
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Assets:
Available-for-sale securities	559,275	3,679
Foreign exchange contracts	130	153
Net Investment Hedge	10,673
Total Assets	570,078	3,832
Liabilities:
Foreign exchange contracts	734	165
Total Liabilities	$ 734	165
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Liabilities:
Acquisition-related contingent consideration		9,400
Total Liabilities		$ 9,400