Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Disaggregation of Revenue [Line Items]
Total revenues	$ 357,195	$ 331,361	$ 679,556	$ 643,775
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, Number of Customers	3	3	2	3
Revenue from Contract with Customer Benchmark [Member] | Customer Concentration Risk | TransUnion, Equifax and Experian customers
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	39.00%	39.00%	38.00%	37.00%
On-premises and SaaS software
Disaggregation of Revenue [Line Items]
Total revenues	$ 149,088	$ 125,551	$ 275,426	$ 252,006
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	18.00%	9.00%	12.00%	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	82.00%	91.00%	88.00%	90.00%
On-Premises | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	52.00%	51.00%	49.00%	52.00%
SaaS Products | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	48.00%	49.00%	51.00%	48.00%
Platform software | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	27.00%	12.00%	22.00%	12.00%
Non-platform software | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	73.00%	88.00%	78.00%	88.00%
Operating Segments | On-premises and SaaS software
Disaggregation of Revenue [Line Items]
Total revenues			$ 275,426	$ 252,006
Americas
Disaggregation of Revenue [Line Items]
Total revenues	$ 279,755	$ 261,459	$ 544,652	$ 510,196
Americas | Revenue from Contract with Customer Benchmark [Member] | Geographic Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	78.00%	79.00%	80.00%	79.00%
EMEA [Member]
Disaggregation of Revenue [Line Items]
Total revenues	$ 35,380	$ 49,675	$ 74,271	$ 95,223
EMEA [Member] | Revenue from Contract with Customer Benchmark [Member] | Geographic Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	10.00%	15.00%	11.00%	15.00%
Asia Pacific [Member]
Disaggregation of Revenue [Line Items]
Total revenues	$ 42,060	$ 20,227	$ 60,633	$ 38,356
Asia Pacific [Member] | Revenue from Contract with Customer Benchmark [Member] | Geographic Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	12.00%	6.00%	9.00%	6.00%
Scores
Disaggregation of Revenue [Line Items]
Total revenues	$ 183,742	$ 168,719	$ 353,229	$ 313,370
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	$ 125,243	$ 119,319	$ 238,211	$ 219,463
Scores | Business to business Scores | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	68.00%	71.00%	67.00%	70.00%
Scores | Business to consumer Scores
Disaggregation of Revenue [Line Items]
Total revenues	$ 58,499	$ 49,400	$ 115,018	$ 93,907
Scores | Business to consumer Scores | Revenue from Contract with Customer Benchmark [Member] | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	32.00%	29.00%	33.00%	30.00%
Scores | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	$ 183,742	$ 168,719	$ 353,229	$ 313,370
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	175,091	161,787	340,803	302,500
Scores | EMEA [Member]
Disaggregation of Revenue [Line Items]
Total revenues	1,252	5,642	2,745	7,355
Scores | Asia Pacific [Member]
Disaggregation of Revenue [Line Items]
Total revenues	7,399	1,290	9,681	3,515
Software
Disaggregation of Revenue [Line Items]
Total revenues	173,453	162,642	326,327	330,405
Software | On-premises and SaaS software
Disaggregation of Revenue [Line Items]
Total revenues	149,088	125,551	275,426	252,006
Software | On-premises and SaaS software | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Total revenues	26,540	11,844	33,699	24,738
Software | On-premises and SaaS software | Transferred over Time
Disaggregation of Revenue [Line Items]
Total revenues	122,548	113,707	241,727	227,268
Software | On-Premises
Disaggregation of Revenue [Line Items]
Total revenues	77,959	63,431	135,254	129,913
Software | SaaS Products
Disaggregation of Revenue [Line Items]
Total revenues	71,129	62,120	140,172	122,093
Software | Platform software
Disaggregation of Revenue [Line Items]
Total revenues	39,802	15,312	61,874	29,437
Software | Non-platform software
Disaggregation of Revenue [Line Items]
Total revenues	109,286	110,239	213,552	222,569
Software | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	173,453	162,642	326,327	330,405
Software | Operating Segments | On-premises and SaaS software
Disaggregation of Revenue [Line Items]
Total revenues	149,088	125,551	275,426	252,006
Software | Americas
Disaggregation of Revenue [Line Items]
Total revenues	104,664	99,672	203,849	207,696
Software | EMEA [Member]
Disaggregation of Revenue [Line Items]
Total revenues	34,128	44,033	71,526	87,868
Software | Asia Pacific [Member]
Disaggregation of Revenue [Line Items]
Total revenues	$ 34,661	$ 18,937	$ 50,952	$ 34,841