Derivative and Hedging Instruments (Details-1)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021 USD ($)		Jun. 30, 2021 USD ($) Dth MWh MW		Dec. 31, 2020 USD ($) Dth MWh MW		Mar. 31, 2021 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Derivative fair values [Abstract]
Collateral posted against derivative positions	$ 2,900,000		$ 2,900,000		$ 0
Other Current Assets [Member]
Derivative fair values [Abstract]
Derivative fair value, net	520,000		520,000		1,162,000		$ 173,000	$ 940,000	$ 430,000	$ 1,100,000
Commodity Contracts And Financial Transimission Rights [Member]
Derivative fair values [Abstract]
Derivative fair value, net	4,100,000		$ 4,100,000		$ 200,000
Commodity Derivative Contracts [Member]
Gross Notional Volume of Open Derivatives
Notional amount, energy measure (in MWh) | MWh			285,120		259,080
Notional amount, decatherm measure (in Dth) | Dth			5,780,000		6,030,000
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis	3,861,000		$ 3,861,000		$ 806,000
Liability Derivatives, fair value, gross basis	190,000		190,000		632,000
Collateral posted against derivative positions	2,913,000		2,913,000		0
Commodity Derivative Contracts [Member] | Other Current Assets [Member]
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis	3,549,000	[1]	3,549,000	[1]	617,000	[2]
Liability Derivatives, fair value, gross basis	184,000	[1]	184,000	[1]	593,000	[2]
Commodity Derivative Contracts [Member] | Other Deferred Charges [Member]
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis	312,000	[1]	312,000	[1]	189,000	[2]
Liability Derivatives, fair value, gross basis	6,000	[1]	6,000	[1]	39,000	[2]
Commodity Derivative Contracts [Member] | Cash Flow Hedging [Member]
Derivative fair values [Abstract]
Collateral posted against derivative positions	$ 2,900,000		$ 2,900,000		$ 0
Energy Related Commodity Contract [Member] | Cash Flow Hedging [Member]
Derivatives Fair Value [Line Items]
Maximum term of derivative hedging contract	4 years
Financial Transmission Rights [Member]
Gross Notional Volume of Open Derivatives
Notional amount, power measure (in MW) | MW			4,541		2,869
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis	$ 398,000		$ 398,000
Liability Derivatives, fair value, gross basis					$ 23,000
Collateral posted against derivative positions	0		0
Financial Transmission Rights [Member] | Other Current Assets [Member]
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis	398,000		398,000
Liability Derivatives, fair value, gross basis	0		$ 0
Financial Transmission Rights [Member] | Other Current Liabilities [Member]
Derivative fair values [Abstract]
Asset Derivatives, fair value, gross basis					0
Liability Derivatives, fair value, gross basis					$ 23,000
PPA [Member]
Gross Notional Volume of Open Derivatives
Notional amount, power measure (in MW) | MW			550		850
Derivative fair values [Abstract]
Derivative fair value, net	(6,700,000)		$ (6,700,000)		$ (14,100,000)
Liability Derivatives, fair value, gross basis	6,650,000		6,650,000		14,140,000
PPA [Member] | Derivative Liability (Current) [Member]
Derivative fair values [Abstract]
Liability Derivatives, fair value, gross basis	6,650,000		6,650,000		10,160,000
PPA [Member] | Derivative Liability (Long-term) [Member]
Derivative fair values [Abstract]
Liability Derivatives, fair value, gross basis	$ 0		$ 0		$ 3,980,000

[1] As of June 30, 2021, collateral of $2.9 million was posted against derivative positions owed to counterparties under a master netting agreement on the consolidated balance sheet.

[2] No collateral was posted against derivative positions as of December 31, 2020.