Segment Information - Additional Information (Detail)	12 Months Ended
	Sep. 30, 2018 Segment customer	Sep. 30, 2017 customer	Sep. 30, 2016
Segment Reporting Information [Line Items]
Number of reportable segments | Segment	3
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	57.00%	59.00%	61.00%
Sales Revenue | Product Concentration Risk | Applications | Fraud Solutions
Segment Reporting Information [Line Items]
Concentration of risk, Percentage	17.00%	19.00%	20.00%
Sales Revenue | Product Concentration Risk | Applications | Customer Cummunication Services
Segment Reporting Information [Line Items]
Concentration of risk, Percentage	10.00%	10.00%	9.00%
Sales Revenue | Product Concentration Risk | Applications | Customer Management Solutions
Segment Reporting Information [Line Items]
Concentration of risk, Percentage	8.00%	8.00%	9.00%
Sales Revenue | Customer Concentration Risk
Segment Reporting Information [Line Items]
Concentration of risk, Percentage	100.00%	100.00%	100.00%
Accounts Receivable | Customer Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk, number of customers | customer	0	0