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Organization and Basis of Presentation - Narrative (Details) mi in Thousands, customer in Thousands, $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2021 USD ($) customer company transmissionCenter mi MW | Mar. 31, 2020 USD ($)
Property, Plant and Equipment [Line Items] |  |
Length of transmission lines | mi | 24 |
Number of regional transmission centers | transmissionCenter | 2 |
Capitalized cost of equity | $ | $ 7 | $ 11
Capitalized interest | $ | $ 6 | $ 7
PN | Waverly, New York |  |
Property, Plant and Equipment [Line Items] |  |
Number of customers served by utility operating companies | customer | 4 |
Regulated Distribution |  |
Property, Plant and Equipment [Line Items] |  |
Number of existing utility operating companies | company | 10 |
Number of customers served by utility operating companies | customer | 6,000 |
Plant capacity (in MW's) | MW | 3,580 |

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- Definition Number Of Customers. + References No definition available. + Details
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- Definition Number of Regional Transmission Centers + References No definition available. + Details
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- Definition Amount of interest capitalized during the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391 + Details
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- Definition The component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501569&loc=d3e55921-110430 + Details
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