Segment Information - Disaggregation of revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 307,971	$ 278,234	$ 606,475	$ 540,490
North America [Member]
Disaggregation of Revenue [Line Items]
Revenues	223,156	204,317	434,406	381,163
Latin America [Member]
Disaggregation of Revenue [Line Items]
Revenues	18,208	11,365	32,342	35,357
EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenues	42,911	41,883	91,498	82,103
Asia Pacific [Member]
Disaggregation of Revenue [Line Items]
Revenues	23,696	20,669	48,229	41,867
On-Premises Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	105,188	107,036	214,845	220,240
SaaS Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	73,635	66,795	147,344	130,164
Scores Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	129,148	104,403	244,286	190,086
Scores
Disaggregation of Revenue [Line Items]
Revenues	129,148	104,403	244,286	190,086
Scores | North America [Member]
Disaggregation of Revenue [Line Items]
Revenues	123,249	100,491	233,446	182,564
Scores | Latin America [Member]
Disaggregation of Revenue [Line Items]
Revenues	2,619	1,368	2,903	1,882
Scores | EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,720	1,472	3,258	3,006
Scores | Asia Pacific [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,560	1,072	4,679	2,634
Scores | On-Premises Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Scores | SaaS Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Scores | Scores Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	129,148	104,403	244,286	190,086
Decision Management Software
Disaggregation of Revenue [Line Items]
Revenues	38,544	32,016	69,732	60,930
Decision Management Software | North America [Member]
Disaggregation of Revenue [Line Items]
Revenues	21,007	16,600	36,594	30,424
Decision Management Software | Latin America [Member]
Disaggregation of Revenue [Line Items]
Revenues	5,917	3,327	10,250	8,552
Decision Management Software | EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenues	6,920	7,173	14,185	13,297
Decision Management Software | Asia Pacific [Member]
Disaggregation of Revenue [Line Items]
Revenues	4,700	4,916	8,703	8,657
Decision Management Software | On-Premises Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	28,847	25,725	52,526	49,334
Decision Management Software | SaaS Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	9,697	6,291	17,206	11,596
Decision Management Software | Scores Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Applications
Disaggregation of Revenue [Line Items]
Revenues	140,279	141,815	292,457	289,474
Applications | North America [Member]
Disaggregation of Revenue [Line Items]
Revenues	78,900	87,226	164,366	168,175
Applications | Latin America [Member]
Disaggregation of Revenue [Line Items]
Revenues	9,672	6,670	19,189	24,923
Applications | EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenues	34,271	33,238	74,055	65,800
Applications | Asia Pacific [Member]
Disaggregation of Revenue [Line Items]
Revenues	17,436	14,681	34,847	30,576
Applications | On-Premises Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	76,341	81,311	162,319	170,906
Applications | SaaS Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	63,938	60,504	130,138	118,568
Applications | Scores Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 0	$ 0	$ 0	$ 0
Revenue from Contract with Customer Benchmark [Member]
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	100.00%	100.00%	100.00%	100.00%
Revenue from Contract with Customer Benchmark [Member] | Scores
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	42.00%	38.00%	40.00%	35.00%
Revenue from Contract with Customer Benchmark [Member] | Decision Management Software
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	12.00%	11.00%	12.00%	11.00%
Revenue from Contract with Customer Benchmark [Member] | Applications
Disaggregation of Revenue [Line Items]
Concentration Risk, Percentage	46.00%	51.00%	48.00%	54.00%