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REVENUES - Operating Revenues Disaggregated by Revenue Source (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | $ 9,815,000 | $ 8,766,500 | $ 8,450,000
Alternative Revenue Programs | 41,700 | 130,000 | 53,200
Other Revenues | 6,400 | 7,900 | 23,300
Operating Revenues | 9,863,085 | 8,904,430 | 8,526,470
Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 5,123,600 | 4,741,500 | 4,411,100
Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 3,041,400 | 2,772,900 | 2,992,000
Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 499,700 | 425,600 | 421,600
Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 8,664,700 | 7,940,000 | 7,824,700
Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 453,200 | 340,900 | 269,400
Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 661,800 | 374,100 | 275,200
Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 114,000 | 111,500 | 80,700
Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (78,700) |  |
The Connecticut Light and Power Company |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating Revenues | 3,637,412 | 3,547,527 | 3,232,551
NSTAR Electric Company |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating Revenues | 3,056,350 | 2,941,148 | 3,044,642
Public Service Company of New Hampshire |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating Revenues | 1,177,248 | 1,079,095 | 1,065,936
Operating Segments | Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 7,404,000 | 7,038,600 | 6,912,100
Alternative Revenue Programs | 14,700 | 88,100 | 45,900
Other Revenues | 4,900 | 5,600 | 18,500
Operating Revenues | 7,423,600 | 7,132,300 | 6,976,500
Operating Segments | Electric Distribution | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 3,989,800 | 3,951,500 | 3,723,700
Operating Segments | Electric Distribution | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 2,486,100 | 2,353,400 | 2,584,800
Operating Segments | Electric Distribution | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 345,300 | 327,100 | 331,800
Operating Segments | Electric Distribution | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 6,821,200 | 6,632,000 | 6,640,300
Operating Segments | Electric Distribution | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Electric Distribution | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 575,800 | 327,300 | 215,700
Operating Segments | Electric Distribution | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 78,100 | 79,300 | 56,100
Operating Segments | Electric Distribution | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (71,100) |  |
Operating Segments | Natural Gas Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,752,300 | 1,162,900 | 1,064,000
Alternative Revenue Programs | 37,000 | 44,700 | (4,900)
Other Revenues | 300 | 1,100 | 3,100
Operating Revenues | 1,789,600 | 1,208,700 | 1,062,200
Operating Segments | Natural Gas Distribution | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,000,300 | 644,900 | 555,100
Operating Segments | Natural Gas Distribution | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 497,600 | 361,900 | 347,600
Operating Segments | Natural Gas Distribution | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 167,200 | 107,400 | 96,900
Operating Segments | Natural Gas Distribution | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,665,100 | 1,114,200 | 999,600
Operating Segments | Natural Gas Distribution | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Natural Gas Distribution | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 82,100 | 43,000 | 55,400
Operating Segments | Natural Gas Distribution | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 5,100 | 5,700 | 9,000
Operating Segments | Natural Gas Distribution | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 |  |
Operating Segments | Electric Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,759,900 | 1,570,600 | 1,306,500
Alternative Revenue Programs | (126,100) | (35,200) | 81,800
Other Revenues | 800 | 700 | 700
Operating Revenues | 1,634,600 | 1,536,100 | 1,389,000
Operating Segments | Electric Transmission | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Electric Transmission | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Electric Transmission | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Electric Transmission | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Electric Transmission | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,751,300 | 1,557,300 | 1,293,300
Operating Segments | Electric Transmission | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Electric Transmission | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 13,600 | 13,300 | 13,200
Operating Segments | Electric Transmission | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (5,000) |  |
Operating Segments | Water Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 209,400 | 219,600 | 209,000
Alternative Revenue Programs | 1,500 | (4,700) | 4,600
Other Revenues | 400 | 500 | 1,000
Operating Revenues | 211,300 | 215,400 | 214,600
Operating Segments | Water Distribution | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 133,500 | 145,100 | 132,300
Operating Segments | Water Distribution | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 62,800 | 62,400 | 63,900
Operating Segments | Water Distribution | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 4,300 | 4,800 | 4,500
Operating Segments | Water Distribution | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 200,600 | 212,300 | 200,700
Operating Segments | Water Distribution | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Water Distribution | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 3,900 | 3,800 | 4,100
Operating Segments | Water Distribution | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 7,500 | 3,500 | 4,200
Operating Segments | Water Distribution | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (2,600) |  |
Operating Segments | The Connecticut Light and Power Company |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 4,238,900 | 4,044,700 | 3,626,900
Alternative Revenue Programs | (78,900) | (4,200) | 77,500
Other Revenues | 400 | 2,200 | 10,300
Operating Segments | The Connecticut Light and Power Company | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,994,200 | 2,011,100 | 1,837,100
Operating Segments | The Connecticut Light and Power Company | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 890,600 | 878,300 | 922,900
Operating Segments | The Connecticut Light and Power Company | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 131,400 | 137,500 | 138,300
Operating Segments | The Connecticut Light and Power Company | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 3,016,200 | 3,026,900 | 2,898,300
Operating Segments | The Connecticut Light and Power Company | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 863,300 | 754,800 | 587,100
Operating Segments | The Connecticut Light and Power Company | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 408,800 | 230,100 | 105,100
Operating Segments | The Connecticut Light and Power Company | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 26,700 | 32,900 | 36,400
Operating Segments | The Connecticut Light and Power Company | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (76,100) | 0 | 0
Operating Segments | NSTAR Electric Company |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 3,541,600 | 3,327,500 | 3,396,400
Alternative Revenue Programs | (15,100) | 54,500 | 41,600
Other Revenues | 3,400 | 3,500 | 7,000
Operating Segments | NSTAR Electric Company | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,375,800 | 1,365,800 | 1,322,100
Operating Segments | NSTAR Electric Company | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,265,000 | 1,176,800 | 1,349,400
Operating Segments | NSTAR Electric Company | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 119,100 | 106,400 | 115,800
Operating Segments | NSTAR Electric Company | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 2,759,900 | 2,649,000 | 2,787,300
Operating Segments | NSTAR Electric Company | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 616,300 | 576,500 | 517,300
Operating Segments | NSTAR Electric Company | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 109,200 | 58,400 | 73,100
Operating Segments | NSTAR Electric Company | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 56,200 | 43,600 | 18,700
Operating Segments | NSTAR Electric Company | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Public Service Company of New Hampshire |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,387,600 | 1,241,300 | 1,200,100
Alternative Revenue Programs | (17,400) | 2,600 | 8,600
Other Revenues | 1,900 | 600 | 1,900
Operating Segments | Public Service Company of New Hampshire | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 619,800 | 574,600 | 564,500
Operating Segments | Public Service Company of New Hampshire | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 332,200 | 299,900 | 314,600
Operating Segments | Public Service Company of New Hampshire | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 94,800 | 83,200 | 77,700
Operating Segments | Public Service Company of New Hampshire | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,046,800 | 957,700 | 956,800
Operating Segments | Public Service Company of New Hampshire | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 271,700 | 226,000 | 188,900
Operating Segments | Public Service Company of New Hampshire | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 57,800 | 38,800 | 37,500
Operating Segments | Public Service Company of New Hampshire | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 11,300 | 14,200 | 15,600
Operating Segments | Public Service Company of New Hampshire | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 4,600 | 1,300
Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,354,000 | 1,235,900 | 1,028,500
Alternative Revenue Programs | 0 | 0 | 0
Other Revenues | 0 | 0 | 0
Operating Revenues | 1,354,000 | 1,235,900 | 1,028,500
Other | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Other | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Other | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Other | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Other | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 86,600 | 74,200 | 61,300
Other | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Other | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,267,400 | 1,161,700 | 967,200
Other | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 |  |
Eliminations |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (2,664,600) | (2,461,100) | (2,070,100)
Alternative Revenue Programs | 114,600 | 37,100 | (74,200)
Other Revenues | 0 | 0 | 0
Operating Revenues | (2,550,000) | (2,424,000) | (2,144,300)
Eliminations | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Eliminations | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (5,100) | (4,800) | (4,300)
Eliminations | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (17,100) | (13,700) | (11,600)
Eliminations | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (22,200) | (18,500) | (15,900)
Eliminations | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (1,384,700) | (1,290,600) | (1,085,200)
Eliminations | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Eliminations | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (1,257,700) | (1,152,000) | (969,000)
Eliminations | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 |  |
Consolidations Eliminations | The Connecticut Light and Power Company |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating Revenues | (523,000) | (495,200) | (482,100)
Consolidations Eliminations | NSTAR Electric Company |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating Revenues | (473,500) | (444,400) | (400,400)
Consolidations Eliminations | Public Service Company of New Hampshire |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating Revenues | $ (194,900) | $ (165,400) | $ (144,700)

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- Definition Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 41 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9038-108599 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130545-203045 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 30 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130543-203045 Reference 9: 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 10: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 40 -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9031-108599 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 924 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 11.L) -URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856 + Details
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