Regulatory Matters (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	May 31, 2021
Regulatory Matters [Line Items]
Approved increase to basic rates and charges	$ 71,000
Total current regulatory assets	112,121	$ 89,419
Total long-term regulatory assets	574,181	541,784
Total current regulatory liabilities	3,956	23,371
Total long-term regulatory liabilities	$ 507,764	$ 527,224
Preferred Resource Portfolio Coal-Fired Generation Retirement MW by 2023	630
Public Utilities, Approved Return on Equity, Percentage	9.90%
Public Utilities, Approved Debt Capital Structure, Percentage	4.90%
Hoosier Wind Project MW	106
Subsidiary, Ownership Percentage, Parent	100.00%
Payments to Acquire Businesses, Gross	$ 92,600
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	48,800
Public Utilities, Rate Bases	$ 3,500,000
Petersburg Unit 1 retired MW			230