Unaudited Condensed Consolidated Balance Sheets - USD ($)	Mar. 31, 2024	Dec. 31, 2023
CURRENT ASSETS:
Cash and cash equivalents	$ 435,217,000	$ 28,579,000
Restricted Cash and Cash Equivalents	5,000
Accounts Receivable, after Allowance for Credit Loss, Current	293,660,000	233,921,000
Accounts Receivable, Allowance for Credit Loss, Current	3,765,000	2,283,000
Inventory, Net	137,005,000	143,590,000
Regulatory assets	112,121,000	89,419,000
Income Taxes Receivable, Current	34,802,000	36,481,000
Derivative Asset	393,000	15,682,000
Other Assets, Current	26,911,000	26,358,000
Total current assets	1,040,109,000	574,030,000
UTILITY PLANT:
Property, Plant and Equipment, Gross	7,210,985,000	7,082,443,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	2,997,620,000	2,954,555,000
Utility plant in service - net	4,213,365,000	4,127,888,000
Construction in Progress, Gross	637,018,000	359,014,000
Total net property, plant and equipment	4,850,383,000	4,486,902,000
Other Assets, Noncurrent [Abstract]
Intangible Assets, Net (Excluding Goodwill)	232,998,000	235,656,000
Regulatory assets	574,181,000	541,784,000
Assets for Plan Benefits, Defined Benefit Plan	40,616,000	41,172,000
Other Assets, Miscellaneous, Noncurrent	277,926,000	301,979,000
Total other non-current assets	1,125,721,000	1,120,591,000
TOTAL ASSETS	7,016,213,000	6,181,523,000
CURRENT LIABILITIES:
Debt, Current	643,922,000	899,159,000
Accounts payable	282,966,000	292,851,000
Accrued taxes	29,022,000	22,580,000
Interest Payable, Current	53,667,000	33,639,000
Customer deposits	27,594,000	29,308,000
Regulatory Liability, Current	3,956,000	23,371,000
Accrued Liabilities and Other Liabilities	20,135,000	27,547,000
Total current liabilities	1,061,262,000	1,328,455,000
Long-term Debt and Lease Obligation	3,677,403,000	2,576,798,000
Deferred Income Tax Liabilities, Net	368,960,000	361,488,000
NON-CURRENT LIABILITIES:
Regulatory Liability, Noncurrent	507,764,000	527,224,000
Accrued other postretirement benefits	2,832,000	2,776,000
Asset retirement obligations	267,872,000	249,930,000
Other non-current liabilities	5,148,000	5,130,000
Total non-current liabilities	4,829,979,000	3,723,346,000
Liabilities	$ 5,891,241,000	$ 5,051,801,000
Common Stock, Shares, Outstanding	108,907,000	108,907,318
Common Stock, Shares Authorized	290,000,000
Common shareholders' equity:
Additional Paid in Capital	$ 1,022,018,000	$ 1,021,992,000
Accumulated Other Comprehensive Income (Loss), Net of Tax	36,680,000	29,294,000
Accumulated deficit	15,624,000	25,182,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,124,972,000	1,129,722,000
Equity, Attributable to Noncontrolling Interest	50,650,000	53,254,000
Total common shareholders' equity	1,074,322,000	1,076,468,000
TOTAL LIABILITIES AND EQUITY	$ 7,016,213,000	$ 6,181,523,000