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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Taxes (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
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Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Schedule of Gross Tax Receipts [Line Items] |  |  |  |
Gross receipts taxes | $ 49.4 | $ 48.4 | $ 137.9 | $ 129.1
CL&P |  |  |  |
Schedule of Gross Tax Receipts [Line Items] |  |  |  |
Gross receipts taxes | $ 46.1 | $ 45.6 | $ 120.7 | $ 114.2

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- Definition The amount of excise and sales taxes included in sales and revenues, which are then deducted as a cost of sales. Includes excise taxes, which are applied to specific types of transactions or items (such as gasoline or alcohol); and sales, use and value added taxes, which are applied to a broad class of revenue-producing transactions involving a wide range of goods and services. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(1)) -URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227 + Details
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