Segment Information - Additional Information (Detail)	12 Months Ended
	Sep. 30, 2016 Segment country customer agency	Sep. 30, 2015 country customer	Sep. 30, 2014 customer
Segment Reporting Information [Line Items]
Number of reportable segments | Segment	3
Geographic Concentration Risk
Segment Reporting Information [Line Items]
Concentration of risk, percentage	100.00%	100.00%	100.00%
Sales Revenue | Product Concentration Risk
Segment Reporting Information [Line Items]
Concentration of risk, percentage	100.00%	100.00%	100.00%
Sales Revenue | Product Concentration Risk | Applications
Segment Reporting Information [Line Items]
Concentration of risk, percentage	61.00%	63.00%	64.00%
Sales Revenue | Product Concentration Risk | Applications | Fraud Solutions
Segment Reporting Information [Line Items]
Concentration of risk, percentage	20.00%	23.00%	23.00%
Sales Revenue | Product Concentration Risk | Applications | Customer Management Solutions
Segment Reporting Information [Line Items]
Concentration of risk, percentage	9.00%	9.00%	10.00%
Sales Revenue | Customer Concentration Risk
Segment Reporting Information [Line Items]
Concentration of risk, percentage	19.00%	16.00%	15.00%
Concentration risk, number of customers	0	0	0
Number of credit reporting agencies substantial revenues derived from | agency	3
Accounts Receivable | Customer Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk, number of customers	0	0
Property Plant and Equipment | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk, number of countries | country	0	0