Segment Information - Summary of Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Segment revenues:
Revenues	$ 298,504	$ 262,256
Segment operating expense	(246,622)	(213,252)
Operating income	51,882	49,004
Unallocated share-based compensation expense	(23,145)	(21,854)
Unallocated amortization expense	(1,796)	(1,502)
Restructuring And Acquisition Related Cost	(3,104)	0
Unallocated interest expense	(9,768)	(9,676)
Unallocated other expense, net	(219)	(2,172)
Income before income taxes	41,895	37,156
Depreciation expense	5,676	6,144
Operating Segments
Segment revenues:
Segment operating expense	(218,577)	(189,896)
Operating income	79,927	72,360
Unallocated Corporate Expenses
Segment revenues:
Segment operating expense	(34,210)	(29,254)
Operating income	(34,210)	(29,254)
Depreciation expense	225	233
Applications
Segment revenues:
Revenues	152,178	147,659
Applications | Operating Segments
Segment revenues:
Revenues	152,178	147,659
Segment operating expense	(116,010)	(107,598)
Operating income	36,168	40,061
Depreciation expense	4,349	4,797
Scores
Segment revenues:
Revenues	115,138	85,683
Scores | Operating Segments
Segment revenues:
Revenues	115,138	85,683
Segment operating expense	(17,712)	(13,482)
Operating income	97,426	72,201
Depreciation expense	116	125
Decision Management Software
Segment revenues:
Revenues	31,188	28,914
Decision Management Software | Operating Segments
Segment revenues:
Revenues	31,188	28,914
Segment operating expense	(50,645)	(39,562)
Operating income	(19,457)	(10,648)
Depreciation expense	986	989
Transactional and Maintenance
Segment revenues:
Revenues	220,374	194,193
Transactional and Maintenance | Applications | Operating Segments
Segment revenues:
Revenues	98,837	97,165
Transactional and Maintenance | Scores | Operating Segments
Segment revenues:
Revenues	107,446	84,821
Transactional and Maintenance | Decision Management Software | Operating Segments
Segment revenues:
Revenues	14,091	12,207
Technology Service
Segment revenues:
Revenues	44,025	40,808
Technology Service | Applications | Operating Segments
Segment revenues:
Revenues	34,023	31,462
Technology Service | Scores | Operating Segments
Segment revenues:
Revenues	264	701
Technology Service | Decision Management Software | Operating Segments
Segment revenues:
Revenues	9,738	8,645
License
Segment revenues:
Revenues	34,105	27,255
License | Applications | Operating Segments
Segment revenues:
Revenues	19,318	19,032
License | Scores | Operating Segments
Segment revenues:
Revenues	7,428	161
License | Decision Management Software | Operating Segments
Segment revenues:
Revenues	$ 7,359	$ 8,062