Goodwill and Intangible Assets - Summary of Changes to Goodwill (Detail) $ in Thousands	6 Months Ended
	Mar. 31, 2019 USD ($)
Goodwill [Roll Forward]
Balance at September 30, 2018	$ 800,890
Addition from acquisitions	980
Foreign currency translation adjustment	(1,174)
Balance at March 31, 2019	800,696
Applications
Goodwill [Roll Forward]
Balance at September 30, 2018	585,161
Addition from acquisitions	980
Foreign currency translation adjustment	(1,254)
Balance at March 31, 2019	584,887
Scores
Goodwill [Roll Forward]
Balance at September 30, 2018	146,648
Addition from acquisitions	0
Foreign currency translation adjustment	0
Balance at March 31, 2019	146,648
Decision Management Software
Goodwill [Roll Forward]
Balance at September 30, 2018	69,081
Addition from acquisitions	0
Foreign currency translation adjustment	80
Balance at March 31, 2019	$ 69,161