Revenues And Percentage Of Revenues By Reportable Market Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting Information [Line Items]
Revenues	$ 221,570	$ 197,610	$ 185,462	$ 184,343	$ 190,327	$ 183,772	$ 179,325	$ 190,020	$ 788,985	$ 743,444	$ 676,423
Concentration of risk, percentage									100.00%	100.00%	100.00%
Applications
Segment Reporting Information [Line Items]
Revenues									504,256	476,084	424,604
Applications | Sales Revenue, Services, Net
Segment Reporting Information [Line Items]
Concentration of risk, percentage									64.00%	64.00%	63.00%
Scores
Segment Reporting Information [Line Items]
Revenues									186,469	180,813	175,623
Scores | Sales Revenue, Services, Net
Segment Reporting Information [Line Items]
Concentration of risk, percentage									24.00%	24.00%	26.00%
Tools
Segment Reporting Information [Line Items]
Revenues									$ 98,260	$ 86,547	$ 76,196
Tools | Sales Revenue, Services, Net
Segment Reporting Information [Line Items]
Concentration of risk, percentage									12.00%	12.00%	11.00%