Segment Information - Summary of Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2016		Sep. 30, 2015		Sep. 30, 2014
Segment revenues:
Transactional and maintenance									$ 605,919		$ 564,232		$ 527,563
Professional services									169,738		151,773		149,834
License									105,699		122,776		111,588
Total revenues	$ 235,824	$ 238,778	$ 206,678	$ 200,076	$ 232,756	$ 209,366	$ 207,109	$ 189,550	881,356		838,781		788,985
Segment operating expense									(711,764)		(701,276)		(627,117)
Operating income									169,592		137,505		161,868
Unallocated share-based compensation expense									(55,509)		(45,308)		(36,362)
Unallocated amortization expense	$ (1,700)	$ (1,900)	$ (1,900)	$ (1,900)	$ (1,800)	$ (1,900)	$ (1,900)	$ (1,800)	(13,982)	[1]	(13,673)	[1]	(11,917)	[1]
Unallocated restructuring and acquisition-related expenses									0		(18,242)		(4,281)
Unallocated interest expense, net									(26,633)		(29,150)		(28,550)
Unallocated other income (expense), net									1,610		883		(187)
Income before income taxes									144,569		109,238		133,131
Depreciation expense									17,651		20,216		20,715
Applications
Segment revenues:
Total revenues									532,642		526,274		504,256
Scores
Segment revenues:
Total revenues									241,059		207,007		186,469
Decision Management Software
Segment revenues:
Total revenues									107,655		105,500		98,260
Operating Segments
Segment revenues:
Segment operating expense									(642,273)		(624,053)		(574,557)
Operating income									239,083		214,728		214,428
Operating Segments | Applications
Segment revenues:
Transactional and maintenance									328,472		320,596		313,316
Professional services									138,775		124,562		121,100
License									65,395		81,116		69,840
Total revenues									532,642				504,256
Segment operating expense									(364,371)		(366,666)		(334,762)
Operating income									168,271		159,608		169,494
Depreciation expense									11,852		13,861		14,451
Operating Segments | Scores
Segment revenues:
Transactional and maintenance									233,655		200,426		178,023
Professional services									4,185		2,901		2,784
License									3,219		3,680		5,662
Total revenues									241,059				186,469
Segment operating expense									(55,975)		(55,793)		(44,187)
Operating income									185,084		151,214		142,282
Depreciation expense									814		921		851
Operating Segments | Decision Management Software
Segment revenues:
Transactional and maintenance									43,792		43,210		36,224
Professional services									26,778		24,310		25,950
License									37,085		37,980		36,086
Total revenues									107,655				98,260
Segment operating expense									(111,315)		(111,850)		(94,057)
Operating income									(3,660)		(6,350)		4,203
Depreciation expense									3,657		3,087		2,752
Unallocated Corporate Expenses
Segment revenues:
Segment operating expense									(110,612)		(89,744)		(101,551)
Operating income									(110,612)		(89,744)		(101,551)
Depreciation expense									$ 1,328		$ 2,347		$ 2,661

[1] Cost of revenues and selling, general and administrative expenses exclude the amortization of intangible assets. See Note 7.