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Property, Plant and Equipment - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Electric Plant in Service
Production	$ 1,469,008	$ 1,412,826
Transmission	820,415	777,613
Distribution	726,159	654,704
General	165,361	144,738
Electric Plant in Service	3,180,943	2,989,881
Construction Work in Progress	231,890	137,212
Total Gross Electric Plant	3,412,833	3,127,093
Less Accumulated Depreciation	899,049	851,148
Net Electric Plant	2,513,784	2,275,945
Nonelectric Property, Plant and Equipment
Nonelectric Property, Plant and Equipment	362,565	311,924
Construction Work in Progress	40,536	38,062
Total Gross Nonelectric Property, Plant and Equipment	403,101	349,986
Less Accumulated Depreciation	224,425	207,556
Net Nonelectric Property, Plant and Equipment	178,676	142,430
Net Property, Plant and Equipment	2,692,460	2,418,375
Equipment
Nonelectric Property, Plant and Equipment
Nonelectric Property, Plant and Equipment	260,307	233,571
Buildings and Leasehold Improvements
Nonelectric Property, Plant and Equipment
Nonelectric Property, Plant and Equipment	88,680	64,753
Land
Nonelectric Property, Plant and Equipment
Nonelectric Property, Plant and Equipment	$ 13,578	$ 13,600

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