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Property, Plant, and Equipment (Details) - USD ($) $ in Thousands | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 8,972,849 | $ 8,300,770 |
Less accumulated depreciation, depletion and amortization | 3,216,461 | 3,133,831 | $ 2,991,486
Net property, plant and equipment | 5,756,388 | 5,166,939 | 4,917,142
Electric |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | 2,295,646 | 2,323,403 | 2,227,145
Natural gas distribution |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | 3,015,164 | 2,868,853 | 2,688,123
Pipeline |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | 1,051,868 | 821,697 | 834,215
Construction materials and contracting |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | 2,347,696 | 2,028,476 | 1,910,562
Construction services |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | 225,758 | 220,796 | 213,370
Other |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | 36,717 | 37,545 | $ 35,213
Regulated Operation | Electric | Electric Generation Equipment |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 1,056,632 | 1,133,390 |
Weighted average depreciable life in years | 48 years |  |
Regulated Operation | Electric | Electric Distribution |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 474,037 | 464,442 |
Weighted average depreciable life in years | 47 years |  |
Regulated Operation | Electric | Electric Transmission |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 562,080 | 524,155 |
Weighted average depreciable life in years | 65 years |  |
Regulated Operation | Electric | Construction in Progress |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 62,781 | 61,766 |
Regulated Operation | Electric | Other Capitalized Property Plant and Equipment |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 140,117 | 139,650 |
Weighted average depreciable life in years | 14 years |  |
Regulated Operation | Natural gas distribution | Construction in Progress |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 21,741 | 16,836 |
Regulated Operation | Natural gas distribution | Other Capitalized Property Plant and Equipment |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 225,272 | 213,976 |
Weighted average depreciable life in years | 14 years |  |
Regulated Operation | Natural gas distribution | Gas Distribution [Member] |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 2,427,779 | 2,302,121 |
Weighted average depreciable life in years | 50 years |  |
Regulated Operation | Natural gas distribution | Gas Transmission [Member] |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 107,721 | 104,695 |
Weighted average depreciable life in years | 60 years |  |
Regulated Operation | Natural gas distribution | Natural gas storage |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 34,997 | 33,014 |
Weighted average depreciable life in years | 39 years |  |
Regulated Operation | Natural gas distribution | General |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 197,653 | 198,211 |
Weighted average depreciable life in years | 14 years |  |
Regulated Operation | Pipeline | Construction in Progress |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 263,640 | 46,690 |
Regulated Operation | Pipeline | Other Capitalized Property Plant and Equipment |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 50,477 | 49,640 |
Weighted average depreciable life in years | 17 years |  |
Regulated Operation | Pipeline | Gas Transmission [Member] |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 673,344 | 665,567 |
Weighted average depreciable life in years | 46 years |  |
Regulated Operation | Pipeline | Gas Storage [Member] |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 57,670 | 52,632 |
Weighted average depreciable life in years | 53 years |  |
Nonregulated Operation | Pipeline | Construction in Progress |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 18 | 4 |
Nonregulated Operation | Pipeline | Other Capitalized Property Plant and Equipment |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 6,719 | 7,164 |
Weighted average depreciable life in years | 10 years |  |
Nonregulated Operation | Construction materials and contracting | Construction in Progress |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 50,425 | 23,803 |
Nonregulated Operation | Construction materials and contracting | Land [Member] |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | 149,066 | 132,948 |
Nonregulated Operation | Construction materials and contracting | Building and Building Improvements [Member] |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 149,262 | 130,417 |
Weighted average depreciable life in years | 21 years |  |
Nonregulated Operation | Construction materials and contracting | Machinery, vehicles and equipment |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 1,414,260 | 1,284,604 |
Weighted average depreciable life in years | 12 years |  |
Nonregulated Operation | Construction materials and contracting | Aggregate reserves [Member] |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 584,683 | 456,704 |
Nonregulated Operation | Construction services | Other Capitalized Property Plant and Equipment |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 13,467 | 8,824 |
Weighted average depreciable life in years | 2 years |  |
Nonregulated Operation | Construction services | Land [Member] |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 6,513 | 7,218 |
Nonregulated Operation | Construction services | Building and Building Improvements [Member] |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 39,039 | 41,674 |
Weighted average depreciable life in years | 24 years |  |
Nonregulated Operation | Construction services | Machinery, vehicles and equipment |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 166,739 | 163,080 |
Weighted average depreciable life in years | 7 years |  |
Nonregulated Operation | Other | Other Capitalized Property Plant and Equipment |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 34,069 | 34,897 |
Weighted average depreciable life in years | 7 years |  |
Nonregulated Operation | Other | Land [Member] |  |  |
Property, plant and equipment [Line Items] |  |  |
Property, Plant and Equipment, Gross | $ 2,648 | $ 2,648 |

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