Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,294,562	$ 1,160,083	$ 1,000,146
North America
Disaggregation of Revenue [Line Items]
Total revenues	929,928	807,165	701,010
Latin America
Disaggregation of Revenue [Line Items]
Total revenues	62,297	65,287	45,537
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	203,584	195,186	169,592
Asia Pacific
Disaggregation of Revenue [Line Items]
Total revenues	98,753	92,445	84,007
On-Premises
Disaggregation of Revenue [Line Items]
Total revenues	465,971	468,552	423,334
SaaS
Disaggregation of Revenue [Line Items]
Total revenues	300,044	270,354	240,942
Scores
Disaggregation of Revenue [Line Items]
Total revenues	528,547	421,177	335,870
Applications
Disaggregation of Revenue [Line Items]
Total revenues	602,046	605,034	564,375
Applications | North America
Disaggregation of Revenue [Line Items]
Total revenues	331,290	338,990	318,836
Applications | Latin America
Disaggregation of Revenue [Line Items]
Total revenues	40,047	42,656	39,136
Applications | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	157,793	155,539	141,358
Applications | Asia Pacific
Disaggregation of Revenue [Line Items]
Total revenues	72,916	67,849	65,045
Applications | On-Premises
Disaggregation of Revenue [Line Items]
Total revenues	340,702	360,105	337,162
Applications | SaaS
Disaggregation of Revenue [Line Items]
Total revenues	261,344	244,929	227,213
Applications | Scores
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0
Scores
Disaggregation of Revenue [Line Items]
Total revenues	528,547	421,177	335,870
Scores | North America
Disaggregation of Revenue [Line Items]
Total revenues	511,333	404,778	328,990
Scores | Latin America
Disaggregation of Revenue [Line Items]
Total revenues	3,576	4,591	1,366
Scores | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	6,385	6,359	3,989
Scores | Asia Pacific
Disaggregation of Revenue [Line Items]
Total revenues	7,253	5,449	1,525
Scores | On-Premises
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0
Scores | SaaS
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0
Scores | Scores
Disaggregation of Revenue [Line Items]
Total revenues	528,547	421,177	335,870
Decision Management Software
Disaggregation of Revenue [Line Items]
Total revenues	163,969	133,872	99,901
Decision Management Software | North America
Disaggregation of Revenue [Line Items]
Total revenues	87,305	63,397	53,184
Decision Management Software | Latin America
Disaggregation of Revenue [Line Items]
Total revenues	18,674	18,040	5,035
Decision Management Software | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	39,406	33,288	24,245
Decision Management Software | Asia Pacific
Disaggregation of Revenue [Line Items]
Total revenues	18,584	19,147	17,437
Decision Management Software | On-Premises
Disaggregation of Revenue [Line Items]
Total revenues	125,269	108,447	86,172
Decision Management Software | SaaS
Disaggregation of Revenue [Line Items]
Total revenues	38,700	25,425	13,729
Decision Management Software | Scores
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ 0	$ 0
Revenue from Contract with Customer Benchmark
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	100.00%	100.00%	100.00%
Revenue from Contract with Customer Benchmark | Non-US [Member]
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	32.00%	34.00%	35.00%
Revenue from Contract with Customer Benchmark | Applications
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	46.00%	52.00%	56.00%
Revenue from Contract with Customer Benchmark | Scores
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	41.00%	36.00%	34.00%
Revenue from Contract with Customer Benchmark | Decision Management Software
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	13.00%	12.00%	10.00%