Leases - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2020	Dec. 31, 2020
Lessee Lease Description [Line Items]
Right-of-use asset impairments		$ 2.3
Leasehold impairments		1.1
Office Space [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]
Right-of-use asset impairments		2.3
Leasehold impairments		$ 1.1

The adjustment to reduce the value of existing agreements that specify the lessee's rights to use the leased property. This expense is charged when the estimates of future profits generated by the leased property are reduced.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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
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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
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