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
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
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-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

Concentrations of Credit Risk (Details) - institution			3 Months Ended		9 Months Ended		12 Months Ended
Concentrations of Credit Risk (Details) - institution	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Concentration Risk [Line Items]
Number of institutions in which company holds its cash and cash equivalents	2						2
Revenue Benchmark \| Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage			100.00%	100.00%	100.00%	100.00%	100.00%	100.00%	100.00%
Revenue Benchmark \| Customer Concentration Risk \| Six Payers
Concentration Risk [Line Items]
Concentration risk percentage			84.00%	85.00%	82.00%	82.00%	75.00%	74.00%	69.00%
Accounts Receivable \| Customer Concentration Risk \| Six Payers
Concentration Risk [Line Items]
Concentration risk percentage	71.00%	70.00%					70.00%	69.00%	68.00%