Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 1,160,083	$ 1,000,146	$ 934,983
North America
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	807,165	701,010	640,244
Latin America
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	65,287	45,537	43,363
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	195,186	169,592	173,818
Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	92,445	84,007	77,558
On-Premises
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	468,552	423,334	472,939
SaaS
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	270,354	240,942	202,507
Scores
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	421,177	335,870	259,537
Applications
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	605,034	564,375	560,634
Applications | North America
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	338,990	318,836	327,226
Applications | Latin America
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	42,656	39,136	34,678
Applications | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	155,539	141,358	139,765
Applications | Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	67,849	65,045	58,965
Applications | On-Premises
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	360,105	337,162	367,944
Applications | SaaS
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	244,929	227,213	192,690
Applications | Scores
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Scores
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	421,177	335,870	259,537
Scores | North America
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	404,778	328,990	250,260
Scores | Latin America
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,591	1,366	1,573
Scores | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	6,359	3,989	3,831
Scores | Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	5,449	1,525	3,873
Scores | On-Premises
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Scores | SaaS
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Scores | Scores
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	421,177	335,870	259,537
Decision Management Software
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	133,872	99,901	114,812
Decision Management Software | North America
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	63,397	53,184	62,758
Decision Management Software | Latin America
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	18,040	5,035	7,112
Decision Management Software | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	33,288	24,245	30,222
Decision Management Software | Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	19,147	17,437	14,720
Decision Management Software | On-Premises
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	108,447	86,172	104,995
Decision Management Software | SaaS
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	25,425	13,729	9,817
Decision Management Software | Scores
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 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	34.00%	35.00%	37.00%
Revenue from Contract with Customer Benchmark | Applications
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	52.00%	56.00%	60.00%
Revenue from Contract with Customer Benchmark | Scores
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	36.00%	34.00%	28.00%
Revenue from Contract with Customer Benchmark | Decision Management Software
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	12.00%	10.00%	12.00%