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Accounts Receivable, net - Narrative (Details) - USD ($) $ in Thousands | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2019 | Sep. 30, 2021 | Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Unbilled revenues accrued |  | $ 21,000 | $ 11,900
Past due receivables outstanding |  | $ 127,699 | $ 107,628
Texas Customer |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Past due receivables outstanding | $ 1,400 |  |
Texas Customer | Litigation and Commercial Claims |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Past due receivables outstanding | 1,400 |  |
Reserve for past due receivables | $ 1,400 |  |

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- Definition Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as current. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=123360276&loc=SL49130531-203044 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=123360276&loc=SL49130533-203044 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130549-203045 + Details
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