Segment Information - Summary of Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Segment revenues:
Total revenues	$ 433,809	$ 380,266	$ 815,868	$ 725,136
Segment operating expense	(238,968)	(220,505)	(469,668)	(425,036)
Operating income	194,841	159,761	346,200	300,100
Unallocated share-based compensation expense	(35,448)	(27,053)	(67,022)	(56,755)
Unallocated amortization expense	(275)	(275)	(550)	(550)
Unallocated interest expense	(26,093)	(23,897)	(50,255)	(46,697)
Unallocated other income, net	3,986	1,605	7,379	1,969
Income before income taxes	172,734	137,469	303,324	255,372
Depreciation expense	2,222	2,881	3,913	6,028
Gain on product line asset sale				1,941
Operating Segments
Segment revenues:
Segment operating expense	(203,245)	(193,177)	(402,096)	(369,672)
Operating income	230,564	187,089	413,772	355,464
Unallocated Corporate Expenses
Segment revenues:
Segment operating expense	(45,806)	(43,183)	(86,374)	(77,265)
Operating income	(45,806)	(43,183)	(86,374)	(77,265)
Depreciation expense	16	20	28	42
Scores
Segment revenues:
Total revenues	236,885	198,507	428,997	376,495
Scores | Operating Segments
Segment revenues:
Total revenues	236,885	198,507	428,997	376,495
Segment operating expense	(24,677)	(23,102)	(48,135)	(44,398)
Operating income	212,208	175,405	380,862	332,097
Depreciation expense	107	138	188	289
Software
Segment revenues:
Total revenues	196,924	181,759	386,871	348,641
Software | Operating Segments
Segment revenues:
Total revenues	196,924	181,759	386,871	348,641
Segment operating expense	(132,762)	(126,892)	(267,587)	(248,009)
Operating income	64,162	54,867	119,284	100,632
Depreciation expense	2,099	2,723	3,697	5,697
Professional services
Segment revenues:
Total revenues	19,744	27,175	41,023	49,497
Professional services | Operating Segments
Segment revenues:
Total revenues			41,023	49,497
Professional services | Scores | Operating Segments
Segment revenues:
Total revenues	0	0	0	0
Professional services | Software | Operating Segments
Segment revenues:
Total revenues	19,744	27,175	41,023	49,497
On-premises and SaaS software
Segment revenues:
Total revenues	177,180	154,584	345,848	299,144
On-premises and SaaS software | Operating Segments
Segment revenues:
Total revenues			345,848	299,144
On-premises and SaaS software | Scores | Operating Segments
Segment revenues:
Total revenues	0	0	0	0
On-premises and SaaS software | Software
Segment revenues:
Total revenues	177,180	154,584	345,848	299,144
On-premises and SaaS software | Software | Operating Segments
Segment revenues:
Total revenues	177,180	154,584	345,848	299,144
Scores
Segment revenues:
Total revenues	236,885	198,507	428,997	376,495
Scores | Operating Segments
Segment revenues:
Total revenues			428,997	376,495
Scores | Scores | Operating Segments
Segment revenues:
Total revenues	236,885	198,507	428,997	376,495
Scores | Software | Operating Segments
Segment revenues:
Total revenues	$ 0	$ 0	$ 0	$ 0