Segment Information - Summary of Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Segment revenues:
Total revenues	$ 382,059	$ 344,870
Segment operating expense	(230,700)	(204,531)
Operating income	151,359	140,339
Unallocated share-based compensation expense	(31,574)	(29,702)
Unallocated amortization expense	(275)	(275)
Unallocated interest expense	(24,162)	(22,800)
Unallocated other income, net	3,393	364
Income before income taxes	130,590	117,903
Depreciation expense	1,691	3,147
Gain on product line asset sale		1,941
Operating Segments
Segment revenues:
Segment operating expense	(198,851)	(176,495)
Operating income	183,208	168,375
Unallocated Corporate Expenses
Segment revenues:
Segment operating expense	(40,568)	(34,082)
Operating income	(40,568)	(34,082)
Depreciation expense	12	22
Scores
Segment revenues:
Total revenues	192,112	177,988
Scores | Operating Segments
Segment revenues:
Total revenues	192,112	177,988
Segment operating expense	(23,458)	(21,296)
Operating income	168,654	156,692
Depreciation expense	81	151
Software
Segment revenues:
Total revenues	189,947	166,882
Software | Operating Segments
Segment revenues:
Total revenues	189,947	166,882
Segment operating expense	(134,825)	(121,117)
Operating income	55,122	45,765
Depreciation expense	1,598	2,974
Professional services
Segment revenues:
Total revenues	21,279	22,322
Professional services | Scores | Operating Segments
Segment revenues:
Total revenues	0	0
Professional services | Software | Operating Segments
Segment revenues:
Total revenues	21,279	22,322
On-premises and SaaS software
Segment revenues:
Total revenues	168,668	144,560
On-premises and SaaS software | Scores | Operating Segments
Segment revenues:
Total revenues	0	0
On-premises and SaaS software | Software
Segment revenues:
Total revenues	168,668	144,560
On-premises and SaaS software | Software | Operating Segments
Segment revenues:
Total revenues	168,668	144,560
Scores
Segment revenues:
Total revenues	192,112	177,988
Scores | Scores | Operating Segments
Segment revenues:
Total revenues	192,112	177,988
Scores | Software | Operating Segments
Segment revenues:
Total revenues	$ 0	$ 0