Segment Information - Summary of Segment Information (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Segment revenues:
Transactional and maintenance		$ 195,195	$ 161,249	$ 369,857	$ 314,909
Professional services		46,078	41,284	88,704	84,827
License		16,585	25,845	34,618	48,242
Total revenues		257,858	228,378	493,179	447,978
Segment operating expense		(209,779)	(188,337)	(405,196)	(373,010)
Operating income		48,079	40,041	87,983	74,968
Unallocated share-based compensation expense		(19,239)	(14,712)	(35,749)	(29,231)
Unallocated amortization expense	[1]	(1,684)	(3,312)	(3,472)	(6,632)
Unallocated interest expense		(7,116)	(6,578)	(13,576)	(12,750)
Unallocated other expense, net		(161)	(327)	352	(427)
Income before income taxes		40,802	33,136	74,759	61,791
Depreciation expense		5,510	5,738	11,304	11,347
Operating Segments
Segment revenues:
Segment operating expense		(188,856)	(170,313)	(365,975)	(337,147)
Operating income		69,002	58,065	127,204	110,831
Unallocated Corporate Expenses
Segment revenues:
Segment operating expense		(33,493)	(25,223)	(60,253)	(49,856)
Operating income		(33,493)	(25,223)	(60,253)	(49,856)
Depreciation expense		238	341	522	690
Applications | Operating Segments
Segment revenues:
Transactional and maintenance		97,630	86,013	190,843	170,894
Professional services		38,516	32,640	73,369	66,981
License		10,553	15,684	23,896	31,227
Total revenues		146,699	134,337	288,108	269,102
Segment operating expense		(107,039)	(99,454)	(209,658)	(199,251)
Operating income		39,660	34,883	78,450	69,851
Depreciation expense		3,834	3,959	7,777	7,827
Scores | Operating Segments
Segment revenues:
Transactional and maintenance		85,644	63,628	155,218	121,880
Professional services		682	994	960	1,515
License		1,584	811	1,647	1,420
Total revenues		87,910	65,433	157,825	124,815
Segment operating expense		(16,411)	(14,484)	(32,298)	(27,803)
Operating income		71,499	50,949	125,527	97,012
Depreciation expense		147	236	302	502
Decision Management Software | Operating Segments
Segment revenues:
Transactional and maintenance		11,921	11,608	23,796	22,135
Professional services		6,880	7,650	14,375	16,331
License		4,448	9,350	9,075	15,595
Total revenues		23,249	28,608	47,246	54,061
Segment operating expense		(31,913)	(31,152)	(63,766)	(60,237)
Operating income		(8,664)	(2,544)	(16,520)	(6,176)
Depreciation expense		$ 1,291	$ 1,202	$ 2,703	$ 2,328

[1] Cost of revenues and selling, general and administrative expenses exclude the amortization of intangible assets. See Note 4.