Disaggregation of Revenue (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2024 USD ($) customer Segment	Jun. 30, 2023 USD ($) Segment	Jun. 30, 2024 USD ($) customer Segment	Jun. 30, 2023 USD ($) Segment	Sep. 30, 2023 customer
Disaggregation of Revenue [Line Items]
Total revenues	$ 447,849	$ 398,688	$ 1,263,717	$ 1,123,824
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)	(3)
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%	42.00%	44.00%	40.00%
Accounts Receivable | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Receivables, Number of Customers | customer	1		1		1
On-premises and SaaS software
Disaggregation of Revenue [Line Items]
Total revenues	$ 183,785	$ 172,059	$ 529,633	$ 471,203
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	13.00%	15.00%	11.00%	12.00%
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	87.00%	85.00%	89.00%	88.00%
On-Premises | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	46.00%	47.00%	45.00%	47.00%
SaaS Products | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	54.00%	53.00%	55.00%	53.00%
Platform software | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	28.00%	23.00%	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	72.00%	77.00%	73.00%	77.00%
Operating Segments | On-premises and SaaS software
Disaggregation of Revenue [Line Items]
Total revenues			$ 529,633	$ 471,203
Americas
Disaggregation of Revenue [Line Items]
Total revenues	$ 381,322	$ 345,399	$ 1,063,849	$ 954,829
Americas | Revenue from Contract with Customer Benchmark [Member] | Geographic Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	85.00%	87.00%	84.00%	85.00%
EMEA
Disaggregation of Revenue [Line Items]
Total revenues	$ 46,361	$ 32,753	$ 124,986	$ 106,446
EMEA | Revenue from Contract with Customer Benchmark [Member] | Geographic Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	10.00%	8.00%	10.00%	9.00%
Asia Pacific
Disaggregation of Revenue [Line Items]
Total revenues	$ 20,166	$ 20,536	$ 74,882	$ 62,549
Asia Pacific | Revenue from Contract with Customer Benchmark [Member] | Geographic Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	5.00%	5.00%	6.00%	6.00%
Scores
Disaggregation of Revenue [Line Items]
Total revenues	$ 241,450	$ 201,778	$ 670,447	$ 578,273
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	$ 188,754	$ 148,128	$ 514,704	$ 417,907
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%	77.00%	72.00%
Scores | Business to consumer Scores
Disaggregation of Revenue [Line Items]
Total revenues	$ 52,696	$ 53,650	$ 155,743	$ 160,366
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%	23.00%	28.00%
Scores | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	$ 241,450	$ 201,778	$ 670,447	$ 578,273
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	239,319	199,948	657,990	570,284
Scores | EMEA
Disaggregation of Revenue [Line Items]
Total revenues	1,769	1,486	4,355	3,988
Scores | Asia Pacific
Disaggregation of Revenue [Line Items]
Total revenues	362	344	8,102	4,001
Software
Disaggregation of Revenue [Line Items]
Total revenues	206,399	196,910	593,270	545,551
Software | On-premises and SaaS software
Disaggregation of Revenue [Line Items]
Total revenues	183,785	172,059	529,633	471,203
Software | On-premises and SaaS software | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Total revenues	24,638	25,077	58,597	56,073
Software | On-premises and SaaS software | Transferred over Time
Disaggregation of Revenue [Line Items]
Total revenues	159,147	146,982	471,036	415,130
Software | On-Premises
Disaggregation of Revenue [Line Items]
Total revenues	83,775	80,770	235,944	219,165
Software | SaaS Products
Disaggregation of Revenue [Line Items]
Total revenues	100,010	91,289	293,689	252,038
Software | Platform software
Disaggregation of Revenue [Line Items]
Total revenues	51,780	40,317	144,278	109,827
Software | Non-platform software
Disaggregation of Revenue [Line Items]
Total revenues	132,005	131,742	385,355	361,376
Software | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	206,399	196,910	593,270	545,551
Software | Operating Segments | On-premises and SaaS software
Disaggregation of Revenue [Line Items]
Total revenues	183,785	172,059	529,633	471,203
Software | Americas
Disaggregation of Revenue [Line Items]
Total revenues	142,003	145,451	405,859	384,545
Software | EMEA
Disaggregation of Revenue [Line Items]
Total revenues	44,592	31,267	120,631	102,458
Software | Asia Pacific
Disaggregation of Revenue [Line Items]
Total revenues	$ 19,804	$ 20,192	$ 66,780	$ 58,548