Segment Information - Revenues And Percentage Of Revenues By Reportable Market Segments (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]
Revenues	$ 232,756	$ 209,366	$ 207,109	$ 189,550	$ 221,570	$ 197,610	$ 185,462	$ 184,343	$ 838,781	$ 788,985	$ 743,444
Product Concentration Risk | Sales Revenue
Segment Reporting Information [Line Items]
Concentration of risk, percentage									100.00%	100.00%	100.00%
Applications
Segment Reporting Information [Line Items]
Revenues									$ 526,274	$ 504,256	$ 476,084
Applications | Product Concentration Risk | Sales Revenue
Segment Reporting Information [Line Items]
Concentration of risk, percentage									63.00%	64.00%	64.00%
Scores
Segment Reporting Information [Line Items]
Revenues									$ 207,007	$ 186,469	$ 180,813
Scores | Product Concentration Risk | Sales Revenue
Segment Reporting Information [Line Items]
Concentration of risk, percentage									25.00%	24.00%	24.00%
Tools
Segment Reporting Information [Line Items]
Revenues									$ 105,500	$ 98,260	$ 86,547
Tools | Product Concentration Risk | Sales Revenue
Segment Reporting Information [Line Items]
Concentration of risk, percentage									12.00%	12.00%	12.00%