Segment Information - Summary of Segment Information (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Segment revenues:
Revenues	$ 312,414,000	$ 298,504,000
Segment operating expense	(217,693,000)	(246,622,000)
Operating income	94,721,000	51,882,000
Unallocated share-based compensation expense	(25,132,000)	(23,145,000)
Unallocated amortization expense	(937,000)	(1,796,000)
Unallocated gain on sale of product line assets	7,334,000	0
Unallocated restructuring and impairment charges	0	(3,104,000)
Unallocated interest expense	(9,641,000)	(9,768,000)
Unallocated other income, net	2,880,000	(219,000)
Income before income taxes	87,960,000	41,895,000
Depreciation expense	5,585,000	5,676,000
Operating Segments
Segment revenues:
Segment operating expense	(198,958,000)	(218,577,000)
Operating income	113,456,000	79,927,000
Unallocated Corporate Expenses
Segment revenues:
Segment operating expense	(30,253,000)	(34,210,000)
Operating income	(30,253,000)	(34,210,000)
Depreciation expense	33,000	225,000
Applications
Segment revenues:
Revenues	135,361,000	152,178,000
Applications | Operating Segments
Segment revenues:
Revenues	135,361,000	152,178,000
Segment operating expense	(99,859,000)	(116,010,000)
Operating income	35,502,000	36,168,000
Depreciation expense	4,374,000	4,349,000
Scores
Segment revenues:
Revenues	144,651,000	115,138,000
Scores | Operating Segments
Segment revenues:
Revenues	144,651,000	115,138,000
Segment operating expense	(21,626,000)	(17,712,000)
Operating income	123,025,000	97,426,000
Depreciation expense	194,000	116,000
Decision Management Software
Segment revenues:
Revenues	32,402,000	31,188,000
Decision Management Software | Operating Segments
Segment revenues:
Revenues	32,402,000	31,188,000
Segment operating expense	(47,220,000)	(50,645,000)
Operating income	(14,818,000)	(19,457,000)
Depreciation expense	984,000	986,000
Transactional and Maintenance
Segment revenues:
Revenues	252,150,000	220,374,000
Transactional and Maintenance | Applications | Operating Segments
Segment revenues:
Revenues	97,731,000	98,837,000
Transactional and Maintenance | Scores | Operating Segments
Segment revenues:
Revenues	138,590,000	107,446,000
Transactional and Maintenance | Decision Management Software | Operating Segments
Segment revenues:
Revenues	15,829,000	14,091,000
Technology Service
Segment revenues:
Revenues	41,425,000	44,025,000
Technology Service | Applications | Operating Segments
Segment revenues:
Revenues	30,605,000	34,023,000
Technology Service | Scores | Operating Segments
Segment revenues:
Revenues	117,000	264,000
Technology Service | Decision Management Software | Operating Segments
Segment revenues:
Revenues	10,703,000	9,738,000
License
Segment revenues:
Revenues	18,839,000	34,105,000
License | Applications | Operating Segments
Segment revenues:
Revenues	7,025,000	19,318,000
License | Scores | Operating Segments
Segment revenues:
Revenues	5,944,000	7,428,000
License | Decision Management Software | Operating Segments
Segment revenues:
Revenues	$ 5,870,000	$ 7,359,000