Acquisitions - Additional Information (Details) $ in Thousands		3 Months Ended			6 Months Ended
	Jan. 15, 2021 USD ($) Employee	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)
Business Acquisition [Line Items]
Business combination, acquisition and transaction related costs		$ 3,900		$ 10,300	$ 5,000	$ 14,200
Borrowings under credit facility					0	600,000
Revenue		505,227		$ 461,785	962,948	$ 890,836
Goodwill, acquired					691
Deferred tax liabilities		4,163			4,163		$ 4,165
Deferred revenue		516,933			516,933		482,131
Accounts receivable		$ 510,196			$ 510,196		$ 541,072
Arena Solutions
Business Acquisition [Line Items]
Payments to acquire business, net of cash	$ 715,000
Cash acquired from acquisition	$ 11,100
Entity number of employees | Employee	170
Revenue			$ 29,800
Fair value adjustments related to purchase accounting for acquisition			$ 9,100
Goodwill, acquired	$ 562,800
Deferred tax liabilities	41,300
Deferred revenue	15,500
Accounts receivable	11,400
Liabilities	400
Arena Solutions | Customer Lists
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 155,000
Acquired finite-lived intangible asset, weighted average useful life	13 years
Arena Solutions | Purchased Software
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 38,300
Acquired finite-lived intangible asset, weighted average useful life	9 years
Arena Solutions | Trademarks
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 4,200
Acquired finite-lived intangible asset, weighted average useful life	12 years
Arena Solutions | Line of Credit
Business Acquisition [Line Items]
Borrowings under credit facility	$ 600,000