Segment Information - Summary of Segment Information (Detail) - USD ($) $ in Thousands		3 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Segment revenues:
Revenues		$ 262,256	$ 232,361
Segment operating expense		(213,252)	(195,536)
Operating income		49,004	36,825
Unallocated share-based compensation expense		(21,854)	(16,510)
Unallocated amortization expense	[1]	(1,502)	(1,788)
Unallocated restructuring and acquisition-related			0
Unallocated interest expense		(9,676)	(6,460)
Unallocated other expense, net		(2,172)	513
Income before income taxes		37,156	30,878
Depreciation expense		6,144	5,794
Operating Segments
Segment revenues:
Segment operating expense		(189,896)	(177,238)
Operating income		72,360	55,123
Unallocated Corporate Expenses
Segment revenues:
Segment operating expense		(29,254)	(26,761)
Operating income		(29,254)	(26,761)
Depreciation expense		233	284
Applications
Segment revenues:
Revenues		147,659	140,174
Applications | Operating Segments
Segment revenues:
Revenues		147,659	140,174
Segment operating expense		(107,598)	(102,726)
Operating income		40,061	37,448
Depreciation expense		4,797	3,943
Scores
Segment revenues:
Revenues		85,683	68,431
Scores | Operating Segments
Segment revenues:
Revenues		85,683	68,431
Segment operating expense		(13,482)	(15,888)
Operating income		72,201	52,543
Depreciation expense		125	155
Decision Management Software
Segment revenues:
Revenues		28,914	23,756
Decision Management Software | Operating Segments
Segment revenues:
Revenues		28,914	23,756
Segment operating expense		(39,562)	(31,863)
Operating income		(10,648)	(8,107)
Depreciation expense		989	1,412
Transactional and Maintenance
Segment revenues:
Revenues		194,193	170,403
Transactional and Maintenance | Applications | Operating Segments
Segment revenues:
Revenues		97,165	91,126
Transactional and Maintenance | Scores | Operating Segments
Segment revenues:
Revenues		84,821	67,996
Transactional and Maintenance | Decision Management Software | Operating Segments
Segment revenues:
Revenues		12,207	11,281
Technology Service
Segment revenues:
Revenues		40,808	43,128
Technology Service | Applications | Operating Segments
Segment revenues:
Revenues		31,462	35,374
Technology Service | Scores | Operating Segments
Segment revenues:
Revenues		701	297
Technology Service | Decision Management Software | Operating Segments
Segment revenues:
Revenues		8,645	7,457
License
Segment revenues:
Revenues		27,255	18,830
License | Applications | Operating Segments
Segment revenues:
Revenues		19,032	13,674
License | Scores | Operating Segments
Segment revenues:
Revenues		161	138
License | Decision Management Software | Operating Segments
Segment revenues:
Revenues		$ 8,062	$ 5,018

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