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Disaggregation of Revenue (Details) - USD ($) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2021 | Mar. 31, 2020
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | $ 630,217 | $ 530,209
Total revenues | 633,432 | 537,050
Services transferred at a point in time |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 6,976 | 6,564
Services transferred over time |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 623,241 | 523,645
Other revenues |  |
Disaggregation of Revenue [Line Items] |  |
Total revenues | 3,215 | 6,841
Retail - Electric , Natural Gas and Coal |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 547,081 | 453,451
Transportation |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 47,841 | 43,969
Wholesale |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 10,163 | 7,407
Market - off-system sales |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 4,845 | 2,366
Transmission/Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 20,287 | 23,016
Inter-company Revenues |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | (39,848) | (38,642)
Total revenues | (40,330) | (39,033)
Inter-company Revenues | Services transferred at a point in time |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | (7,107) | (7,839)
Inter-company Revenues | Services transferred over time |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | (32,741) | (30,803)
Inter-company Revenues | Other revenues |  |
Disaggregation of Revenue [Line Items] |  |
Total revenues | (482) | (391)
Inter-company Revenues | Retail - Electric , Natural Gas and Coal |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | (7,107) | (7,839)
Inter-company Revenues | Transportation |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | (110) | (139)
Inter-company Revenues | Wholesale |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | (24,451) | (23,612)
Inter-company Revenues | Market - off-system sales |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | (2,884) | (2,639)
Inter-company Revenues | Transmission/Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | (5,296) | (4,413)
Electric Utilities |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 227,271 | 173,916
Total revenues | 227,408 | 174,139
Electric Utilities | Services transferred at a point in time |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 0 | 0
Electric Utilities | Services transferred over time |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 227,271 | 173,916
Electric Utilities | Other revenues |  |
Disaggregation of Revenue [Line Items] |  |
Total revenues | 137 | 223
Electric Utilities | Retail - Electric , Natural Gas and Coal |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 198,500 | 148,640
Electric Utilities | Transportation |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 0 | 0
Electric Utilities | Wholesale |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 5,922 | 5,552
Electric Utilities | Market - off-system sales |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 7,656 | 4,867
Electric Utilities | Transmission/Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 15,193 | 14,857
Gas Utilities |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 400,019 | 355,065
Total revenues | 402,519 | 360,773
Gas Utilities | Services transferred at a point in time |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 0 | 0
Gas Utilities | Services transferred over time |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 400,019 | 355,065
Gas Utilities | Other revenues |  |
Disaggregation of Revenue [Line Items] |  |
Total revenues | 2,500 | 5,708
Gas Utilities | Retail - Electric , Natural Gas and Coal |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 341,605 | 298,247
Gas Utilities | Transportation |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 47,951 | 44,108
Gas Utilities | Wholesale |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 0 | 0
Gas Utilities | Market - off-system sales |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 73 | 138
Gas Utilities | Transmission/Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 10,390 | 12,572
Power Generation |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 28,692 | 25,467
Total revenues | 29,163 | 25,966
Power Generation | Services transferred at a point in time |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 0 | 0
Power Generation | Services transferred over time |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 28,692 | 25,467
Power Generation | Other revenues |  |
Disaggregation of Revenue [Line Items] |  |
Total revenues | 471 | 499
Power Generation | Retail - Electric , Natural Gas and Coal |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 0 | 0
Power Generation | Transportation |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 0 | 0
Power Generation | Wholesale |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 28,692 | 25,467
Power Generation | Market - off-system sales |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 0 | 0
Power Generation | Transmission/Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 0 | 0
Mining |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 14,083 | 14,403
Total revenues | 14,672 | 15,205
Mining | Services transferred at a point in time |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 14,083 | 14,403
Mining | Services transferred over time |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 0 | 0
Mining | Other revenues |  |
Disaggregation of Revenue [Line Items] |  |
Total revenues | 589 | 802
Mining | Retail - Electric , Natural Gas and Coal |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 14,083 | 14,403
Mining | Transportation |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 0 | 0
Mining | Wholesale |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 0 | 0
Mining | Market - off-system sales |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | 0 | 0
Mining | Transmission/Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from contracts with customers | $ 0 | $ 0

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