Revenue from Contracts with Customers - Disaggregated Revenue (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2024 USD ($) customer	Sep. 30, 2023 USD ($) customer	Sep. 30, 2022 USD ($) customer
Disaggregation of Revenue [Line Items]
Revenue	$ 1,717,526	$ 1,513,557	$ 1,377,270
Revenue from Contract with Customer Benchmark | Geographic Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	100.00%	100.00%	100.00%
Revenue from Contract with Customer Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration risk, number of customers | customer	3	2	2
Accounts Receivable | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration risk, number of customers | customer	1
Scores
Disaggregation of Revenue [Line Items]
Revenue	$ 919,650	$ 773,828	$ 706,643
Software
Disaggregation of Revenue [Line Items]
Revenue	$ 797,876	$ 739,729	$ 670,627
TransUnion Equifax and Experian customers | Revenue from Contract with Customer Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	45.00%	41.00%	39.00%
On-Premises Software
Disaggregation of Revenue [Line Items]
Revenue	$ 313,632	$ 292,763	$ 280,649
On-Premises Software | Revenue from Contract with Customer Benchmark | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	44.00%	46.00%	50.00%
SaaS Software
Disaggregation of Revenue [Line Items]
Revenue	$ 397,708	$ 347,419	$ 284,102
SaaS Software | Revenue from Contract with Customer Benchmark | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	56.00%	54.00%	50.00%
On-premises and SaaS software
Disaggregation of Revenue [Line Items]
Revenue	$ 711,340	$ 640,182	$ 564,751
On-premises and SaaS software | Revenue from Contract with Customer Benchmark | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	100.00%	100.00%	100.00%
On-premises and SaaS software | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue	$ 76,284	$ 72,843	$ 75,647
On-premises and SaaS software | Transferred at Point in Time | Revenue from Contract with Customer Benchmark | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	11.00%	11.00%	13.00%
On-premises and SaaS software | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenue	$ 635,056	$ 567,339	$ 489,104
On-premises and SaaS software | Transferred over Time | Revenue from Contract with Customer Benchmark | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	89.00%	89.00%	87.00%
Platform Software
Disaggregation of Revenue [Line Items]
Revenue	$ 200,004	$ 154,750	$ 116,252
Platform Software | Revenue from Contract with Customer Benchmark | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	28.00%	24.00%	21.00%
Non-Platform Software
Disaggregation of Revenue [Line Items]
Revenue	$ 511,336	$ 485,432	$ 448,499
Non-Platform Software | Revenue from Contract with Customer Benchmark | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	72.00%	76.00%	79.00%
Business-to-business Scores
Disaggregation of Revenue [Line Items]
Revenue	$ 711,843	$ 560,995	$ 475,442
Business-to-business Scores | Revenue from Contract with Customer Benchmark | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	77.00%	72.00%	67.00%
Business-to-consumer Scores
Disaggregation of Revenue [Line Items]
Revenue	$ 207,807	$ 212,833	$ 231,201
Business-to-consumer Scores | Revenue from Contract with Customer Benchmark | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	23.00%	28.00%	33.00%
Scores Products
Disaggregation of Revenue [Line Items]
Revenue	$ 919,650	$ 773,828	$ 706,643
Scores Products | Revenue from Contract with Customer Benchmark | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	100.00%	100.00%	100.00%
Americas
Disaggregation of Revenue [Line Items]
Revenue	$ 1,449,888	$ 1,286,950	$ 1,130,711
Americas | Revenue from Contract with Customer Benchmark | Geographic Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	84.00%	85.00%	82.00%
Americas | Scores
Disaggregation of Revenue [Line Items]
Revenue	$ 905,266	$ 763,874	$ 691,006
Americas | Software
Disaggregation of Revenue [Line Items]
Revenue	544,622	523,076	439,705
EMEA
Disaggregation of Revenue [Line Items]
Revenue	$ 169,526	$ 141,364	$ 147,299
EMEA | Revenue from Contract with Customer Benchmark | Geographic Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	10.00%	9.00%	11.00%
EMEA | Scores
Disaggregation of Revenue [Line Items]
Revenue	$ 5,908	$ 5,802	$ 4,475
EMEA | Software
Disaggregation of Revenue [Line Items]
Revenue	163,618	135,562	142,824
Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue	$ 98,112	$ 85,243	$ 99,260
Asia Pacific | Revenue from Contract with Customer Benchmark | Geographic Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	6.00%	6.00%	7.00%
Asia Pacific | Scores
Disaggregation of Revenue [Line Items]
Revenue	$ 8,476	$ 4,152	$ 11,162
Asia Pacific | Software
Disaggregation of Revenue [Line Items]
Revenue	$ 89,636	$ 81,091	$ 88,098