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v3.23.2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) customer in Millions |  |  | 3 Months Ended | 6 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
May 26, 2023 USD ($) | May 25, 2023 USD ($) a mile project | Jun. 30, 2023 USD ($) mi² project mile | Mar. 31, 2023 USD ($) | Jun. 30, 2022 USD ($) | Jun. 30, 2023 USD ($) mi² customer project mile regulatedUtility | Jun. 30, 2022 USD ($) | Dec. 31, 2022 USD ($) | Mar. 31, 2022 USD ($) | Dec. 31, 2021 USD ($)
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Number of electric, natural gas and water customers | customer |  |  |  |  |  | 4.4 |  |  |  |
Allowance for uncollectible accounts for late fees and other receivable amounts |  |  | $ 532,400,000 | $ 535,100,000 | $ 457,800,000 | $ 532,400,000 | $ 457,800,000 | $ 486,300,000 | $ 432,200,000 | $ 417,400,000
Number of offshore wind projects | project |  | 3 | 3 |  |  | 3 |  |  |  |
Payments for investment |  |  |  |  |  | $ 390,002,000 | 277,001,000 |  |  |
Impairment charge |  |  | $ 401,000,000 |  | 0 | 401,000,000 | 0 |  |  |
After-tax impairment |  |  | 331,000,000 |  |  |  |  |  |  |
Valuation allowance |  |  | 40,000,000 |  |  | 40,000,000 |  |  |  |
Energy Relief Fund - Merrimack Valley Programs |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Restricted cash, current |  |  | 20,000,000 |  |  | 20,000,000 |  | 20,000,000 |  |
Restricted cash, noncurrent |  |  | 14,400,000 |  |  | 14,400,000 |  | 15,900,000 |  |
COVID-19 |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Allowance for uncollectible accounts for late fees and other receivable amounts |  |  | 50,900,000 |  |  | 50,900,000 |  | 50,900,000 |  |
CL&P |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Allowance for uncollectible accounts for late fees and other receivable amounts |  |  | 262,800,000 | 253,400,000 | 192,700,000 | $ 262,800,000 | 192,700,000 | 225,300,000 | 180,500,000 | 181,300,000
Period of accounts receivable recoverable under financial or medical duress |  |  |  |  |  | 180 days |  |  |  |
CL&P | COVID-19 |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Allowance for uncollectible accounts for late fees and other receivable amounts |  |  | 16,000,000 |  |  | $ 16,000,000 |  | 16,000,000 |  |
NSTAR Electric |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Allowance for uncollectible accounts for late fees and other receivable amounts |  |  | 97,800,000 | 94,600,000 | 100,500,000 | 97,800,000 | 100,500,000 | 95,000,000.0 | 94,800,000 | 97,000,000.0
NSTAR Electric | COVID-19 |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Allowance for uncollectible accounts for late fees and other receivable amounts |  |  | 4,100,000 |  |  | 4,100,000 |  | 4,100,000 |  |
PSNH |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Allowance for uncollectible accounts for late fees and other receivable amounts |  |  | 12,700,000 | 33,500,000 | $ 27,300,000 | 12,700,000 | $ 27,300,000 | 29,200,000 | $ 26,200,000 | $ 24,300,000
PSNH | COVID-19 |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Allowance for uncollectible accounts for late fees and other receivable amounts |  |  | $ 0 |  |  | $ 0 |  | $ 0 |  |
Yankee Gas |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Period of accounts receivable recoverable under financial or medical duress |  |  |  |  |  | 90 days |  |  |  |
Connecticut, Massachusetts and New Hampshire |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Number of regulated utilities | regulatedUtility |  |  |  |  |  | 12 |  |  |  |
Offshore Wind Business |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Ownership interest (percent) |  | 50.00% | 50.00% |  |  | 50.00% |  |  |  |
Lease area off coasts of Massachusetts and Rhode Island (in square miles) | mi² |  |  | 257 |  |  | 257 |  |  |  |
Adjacent lease area (in square miles) | mi² |  |  | 300 |  |  | 300 |  |  |  |
Number of miles off south coast of Massachusetts | mile |  |  | 25 |  |  | 25 |  |  |  |
North East Offshore |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Ownership interest (percent) |  |  | 50.00% |  |  | 50.00% |  |  |  |
Renewable Energy Investment Fund |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Ownership interest (percent) |  |  | 90.00% |  |  | 90.00% |  |  |  |
Proceeds from sale of equity method investments |  |  | $ 23,600,000 | $ 123,400,000 |  | $ 147,000,000 |  |  |  |
Renewable Energy Investment Fund | Equity Method Investee |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Charitable contributions |  |  | $ 20,000,000 |  |  |  |  |  |  |
Uncommitted Lease Area |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Ownership interest (percent) |  | 50.00% |  |  |  |  |  |  |  |
Uncommitted area of developable acres (in acres) | a |  | 175,000 |  |  |  |  |  |  |  |
Number of miles off south coast of Massachusetts | mile |  | 25 |  |  |  |  |  |  |  |
Payments for investment |  | $ 625,000,000 |  |  |  |  |  |  |  |
Uncommitted Lease Area | Orsted |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Ownership interest (percent) |  | 50.00% |  |  |  |  |  |  |  |
South Fork Wind, LLC |  |  |  |  |  |  |  |  |  |
Summary of Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |
Ownership interest (percent) |  | 50.00% | 50.00% |  |  | 50.00% |  |  |  |
Payments for investment | $ 575,000,000 |  |  |  |  |  |  |  |  |
Payments For Equity Method Investments, Percentage Returned |  | 0.5 |  |  |  |  |  |  |  |

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