Fair Value Measurements - Unobservable Input (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2020 USD ($) $ / MWh	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Firm Storage and Peaking Service [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term Purchase Commitment, Demand Charges		$ 136,400,000	$ 135,800,000	$ 125,100,000
Combustion turbines
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term Purchase Commitment, Demand Charges		$ 52,800,000	$ 51,200,000	$ 51,200,000
Minimum | Wells Project [Member] | Income Approach Valuation Technique
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Power prices (per MWh) | $ / MWh	10.23
Fair Value Inputs, Power Contract Costs	$ 6,308
Maximum | Wells Project [Member] | Income Approach Valuation Technique
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Power prices (per MWh) | $ / MWh	38.84
Fair Value Inputs, Power Contract Costs	$ 7,085
Weighted Average | Wells Project [Member] | Income Approach Valuation Technique
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Power prices (per MWh) | $ / MWh	24.43
Fair Value Inputs, Power Contract Costs	$ 6,468