Disaggregation of Revenue (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2024 USD ($) Segment customer	Mar. 31, 2023 USD ($) Segment	Mar. 31, 2024 USD ($) Segment customer	Mar. 31, 2023 USD ($) Segment	Sep. 30, 2023 customer
Disaggregation of Revenue [Line Items]
Total revenues	$ 433,809	$ 380,266	$ 815,868	$ 725,136
Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	100.00%	100.00%	100.00%	100.00%
Revenue from Contract with Customer Benchmark [Member] | Geographic Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	100.00%	100.00%	100.00%	100.00%
Revenue from Contract with Customer Benchmark [Member] | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Revenue, Number of Customers | Segment	(3)	(3)	(3)	(2)
Revenue from Contract with Customer Benchmark [Member] | Customer Concentration Risk | TransUnion, Equifax and Experian customers
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	47.00%	43.00%	43.00%	40.00%
Accounts Receivable | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Receivables, Number of Customers | customer	2		2		1
On-premises and SaaS software
Disaggregation of Revenue [Line Items]
Total revenues	$ 177,180	$ 154,584	$ 345,848	$ 299,144
On-premises and SaaS software | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	100.00%	100.00%	100.00%	100.00%
On-premises and SaaS software | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	11.00%	12.00%	10.00%	10.00%
On-premises and SaaS software | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk | Transferred over Time
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	89.00%	88.00%	90.00%	90.00%
On-Premises | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	45.00%	48.00%	44.00%	46.00%
SaaS Products | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	55.00%	52.00%	56.00%	54.00%
Platform software | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	27.00%	25.00%	27.00%	23.00%
Non-platform software | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	73.00%	75.00%	73.00%	77.00%
Operating Segments | On-premises and SaaS software
Disaggregation of Revenue [Line Items]
Total revenues			$ 345,848	$ 299,144
Americas
Disaggregation of Revenue [Line Items]
Total revenues	$ 364,017	$ 318,303	$ 682,527	$ 609,430
Americas | Revenue from Contract with Customer Benchmark [Member] | Geographic Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	84.00%	84.00%	84.00%	84.00%
EMEA
Disaggregation of Revenue [Line Items]
Total revenues	$ 42,257	$ 41,353	$ 78,625	$ 73,693
EMEA | Revenue from Contract with Customer Benchmark [Member] | Geographic Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	10.00%	11.00%	9.00%	10.00%
Asia Pacific
Disaggregation of Revenue [Line Items]
Total revenues	$ 27,535	$ 20,610	$ 54,716	$ 42,013
Asia Pacific | Revenue from Contract with Customer Benchmark [Member] | Geographic Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	6.00%	5.00%	7.00%	6.00%
Scores
Disaggregation of Revenue [Line Items]
Total revenues	$ 236,885	$ 198,507	$ 428,997	$ 376,495
Scores | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	100.00%	100.00%	100.00%	100.00%
Scores | Business to business Scores
Disaggregation of Revenue [Line Items]
Total revenues	$ 185,508	$ 144,874	$ 325,950	$ 269,779
Scores | Business to business Scores | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	78.00%	73.00%	76.00%	72.00%
Scores | Business to consumer Scores
Disaggregation of Revenue [Line Items]
Total revenues	$ 51,377	$ 53,633	$ 103,047	$ 106,716
Scores | Business to consumer Scores | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	22.00%	27.00%	24.00%	28.00%
Scores | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	$ 236,885	$ 198,507	$ 428,997	$ 376,495
Scores | Operating Segments | On-premises and SaaS software
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Scores | Americas
Disaggregation of Revenue [Line Items]
Total revenues	233,723	197,039	418,671	370,336
Scores | EMEA
Disaggregation of Revenue [Line Items]
Total revenues	1,278	1,154	2,586	2,502
Scores | Asia Pacific
Disaggregation of Revenue [Line Items]
Total revenues	1,884	314	7,740	3,657
Software
Disaggregation of Revenue [Line Items]
Total revenues	196,924	181,759	386,871	348,641
Software | On-premises and SaaS software
Disaggregation of Revenue [Line Items]
Total revenues	177,180	154,584	345,848	299,144
Software | On-premises and SaaS software | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Total revenues	20,177	19,193	33,959	30,996
Software | On-premises and SaaS software | Transferred over Time
Disaggregation of Revenue [Line Items]
Total revenues	157,003	135,391	311,889	268,148
Software | On-Premises
Disaggregation of Revenue [Line Items]
Total revenues	79,697	73,473	152,169	138,395
Software | SaaS Products
Disaggregation of Revenue [Line Items]
Total revenues	97,483	81,111	193,679	160,749
Software | Platform software
Disaggregation of Revenue [Line Items]
Total revenues	47,325	38,682	92,498	69,510
Software | Non-platform software
Disaggregation of Revenue [Line Items]
Total revenues	129,855	115,902	253,350	229,634
Software | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	196,924	181,759	386,871	348,641
Software | Operating Segments | On-premises and SaaS software
Disaggregation of Revenue [Line Items]
Total revenues	177,180	154,584	345,848	299,144
Software | Americas
Disaggregation of Revenue [Line Items]
Total revenues	130,294	121,264	263,856	239,094
Software | EMEA
Disaggregation of Revenue [Line Items]
Total revenues	40,979	40,199	76,039	71,191
Software | Asia Pacific
Disaggregation of Revenue [Line Items]
Total revenues	$ 25,651	$ 20,296	$ 46,976	$ 38,356