Leases - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Dec. 31, 2020	Sep. 30, 2020
Office Space [Member] \| Scenario, Forecast [Member]
Lessee Lease Description [Line Items]
Variable incentive payment received	$ 3.5
Topic 842 [Member] \| SiriusDecisions, Inc [Member] \| Facility Lease [Member]
Lessee Lease Description [Line Items]
Operating lease right-of-use asset impairments		$ 1.4

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No definition available.

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- Definition

Amount of loss from impairment of right-of-use asset from operating lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 25
-Paragraph 6
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121593497&loc=SL77918431-209957

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- Definition

Amount of variable lease payments from operating, direct financing, and sales-type leases, excluding amount included in measurement of lease receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121576215&loc=SL77919372-209981

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