Goodwill and Intangible Assets - Summary of Changes to Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Goodwill [Roll Forward]
Beginning Balance	$ 803,542	$ 800,890
Goodwill, Acquired During Period		11,233
Foreign currency translation adjustment	8,822	(8,581)
Ending Balance	812,364	803,542
Applications
Goodwill [Roll Forward]
Beginning Balance	588,614	585,161
Goodwill, Acquired During Period		11,233
Foreign currency translation adjustment	8,190	(7,780)
Ending Balance	596,804	588,614
Scores
Goodwill [Roll Forward]
Beginning Balance	146,648	146,648
Goodwill, Acquired During Period		0
Foreign currency translation adjustment	0	0
Ending Balance	146,648	146,648
Decision Management Software
Goodwill [Roll Forward]
Beginning Balance	68,280	69,081
Goodwill, Acquired During Period		0
Foreign currency translation adjustment	632	(801)
Ending Balance	$ 68,912	$ 68,280