For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9054-108599

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6351-108592

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=123594938&loc=d3e13531-108611

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 825
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-Subparagraph (a)
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Revenue - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
Revenue - Additional Information (Detail) - USD ($)	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Contract with customer, liability	$ 0		$ 0		$ 0
Customer Concentration Risk [Member] \| Revenue from Contract with Customer Benchmark [Member] \| Customer [Member]
Disaggregation of Revenue [Line Items]
Concentration risk, percentage	10.00%	10.00%	10.00%	10.00%
Customer Concentration Risk [Member] \| Accounts Receivable [Member] \| Customer [Member]
Disaggregation of Revenue [Line Items]
Concentration risk, percentage			10.00%		10.00%
Other Current Assets [Member]
Disaggregation of Revenue [Line Items]
Deferred commissions current	$ 2,900,000		$ 2,900,000		$ 3,300,000
Other Noncurrent Assets [Member]
Disaggregation of Revenue [Line Items]
Deferred commissions non-current	$ 2,500,000		$ 2,500,000		$ 2,100,000