Goodwill and Intangible Assets - Summary of Changes to Goodwill (Detail) $ in Thousands	6 Months Ended
	Mar. 31, 2020 USD ($)
Goodwill [Roll Forward]
Balance at September 30, 2019	$ 803,542
Foreign currency translation adjustment	1,108
Balance at March 31, 2020	804,650
Applications
Goodwill [Roll Forward]
Balance at September 30, 2019	588,614
Foreign currency translation adjustment	1,006
Balance at March 31, 2020	589,620
Scores
Goodwill [Roll Forward]
Balance at September 30, 2019	146,648
Foreign currency translation adjustment	0
Balance at March 31, 2020	146,648
Decision Management Software
Goodwill [Roll Forward]
Balance at September 30, 2019	68,280
Foreign currency translation adjustment	102
Balance at March 31, 2020	$ 68,382