Segment Information - Summary of Segment Information (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment revenues:
Revenues		$ 314,249	$ 254,993	$ 854,739	$ 743,614
Segment operating expense		(228,541)	(210,456)	(671,478)	(615,813)
Operating income		85,708	44,537	183,261	127,801
Unallocated share-based compensation expense		(19,595)	(18,882)	(61,931)	(54,631)
Unallocated amortization expense	[1]	(1,448)	(1,571)	(4,453)	(5,043)
Unallocated interest expense		(10,111)	(8,223)	(29,795)	(21,799)
Unallocated other income, net		2,457	1,588	1,718	1,940
Income before income taxes		78,054	37,902	155,184	107,942
Depreciation expense		6,179	5,348	18,318	16,652
Operating Segments
Segment revenues:
Segment operating expense		(207,498)	(190,003)	(605,094)	(556,139)
Operating income		106,751	64,990	249,645	187,475
Unallocated Corporate Expenses
Segment revenues:
Segment operating expense		(36,019)	(31,922)	(104,779)	(92,176)
Operating income		(36,019)	(31,922)	(104,779)	(92,176)
Depreciation expense		222	215	684	737
Applications
Segment revenues:
Revenues		165,637	138,658	455,111	425,328
Applications | Operating Segments
Segment revenues:
Revenues		165,637	138,658	455,111	425,328
Segment operating expense		(113,400)	(106,741)	(332,641)	(316,759)
Operating income		52,237	31,917	122,470	108,569
Depreciation expense		4,800	3,682	14,259	11,459
Scores
Segment revenues:
Revenues		115,146	90,829	305,232	246,363
Scores | Operating Segments
Segment revenues:
Revenues		115,146	90,829	305,232	246,363
Segment operating expense		(15,850)	(16,369)	(45,499)	(48,670)
Operating income		99,296	74,460	259,733	197,693
Depreciation expense		130	130	387	432
Decision Management Software
Segment revenues:
Revenues		33,466	25,506	94,396	71,923
Decision Management Software | Operating Segments
Segment revenues:
Revenues		33,466	25,506	94,396	71,923
Segment operating expense		(42,229)	(34,971)	(122,175)	(98,534)
Operating income		(8,763)	(9,465)	(27,779)	(26,611)
Depreciation expense		1,027	1,321	2,988	4,024
Transactional and Maintenance
Segment revenues:
Revenues		226,040	192,143	632,012	555,337
Transactional and Maintenance | Applications | Operating Segments
Segment revenues:
Revenues		100,385	91,102	294,624	277,743
Transactional and Maintenance | Scores | Operating Segments
Segment revenues:
Revenues		112,949	89,876	300,133	243,323
Transactional and Maintenance | Decision Management Software | Operating Segments
Segment revenues:
Revenues		12,706	11,165	37,255	34,271
Technology Service
Segment revenues:
Revenues		44,594	42,836	135,957	132,695
Technology Service | Applications | Operating Segments
Segment revenues:
Revenues		33,989	33,783	101,432	108,288
Technology Service | Scores | Operating Segments
Segment revenues:
Revenues		392	559	1,994	1,613
Technology Service | Decision Management Software | Operating Segments
Segment revenues:
Revenues		10,213	8,494	32,531	22,794
License
Segment revenues:
Revenues		43,615	20,014	86,770	55,582
License | Applications | Operating Segments
Segment revenues:
Revenues		31,263	13,773	59,055	39,297
License | Scores | Operating Segments
Segment revenues:
Revenues		1,805	394	3,105	1,427
License | Decision Management Software | Operating Segments
Segment revenues:
Revenues		$ 10,547	$ 5,847	$ 24,610	$ 14,858

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