Commitments And Contingencies (Narrative) (Details) Mcf in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) $ / kWh contract item Mcf	Dec. 31, 2016 USD ($)
Other Commitments [Line Items]
Contingency accruals	$ 0
Percentage of power generated from gas	81.00%	77.00%
Patronage capital payable, noncurrent	$ 8,798,077	$ 12,008,499
Other current liabilities	$ 7,079,821	$ 3,234,586
Regulatory initial cost charge per KWH | $ / kWh	0.000626
Regulatory current cost charge per KWH | $ / kWh	0.000899
Percentage of three year average of gross retail revenue to be spent on underground lines	2.00%
Average of gross revenue to determine expenditure for underground lines	3 years
Percentage of retail bill collected to move existing overhead lines underground	2.00%
Beluga Power Plant [Member]
Other Commitments [Line Items]
Percentage of power generated from gas	14.00%	9.00%
Southcentral Power Project Plant [Member]
Other Commitments [Line Items]
Percentage of power generated from gas	81.00%	88.00%
Homer Electric Association, Inc. [Member]
Other Commitments [Line Items]
Power contracts expiration date	Dec. 31, 2013
Patronage capital, annual retirements	$ 2,000,000
Payments to retire patronage capital	2,000,000
Patronage capital payable, noncurrent	3,900,000	$ 7,900,000
Patronage capital payable, current	2,000,000
Matanuska Electric Association, Inc. [Member]
Other Commitments [Line Items]
Payments to retire patronage capital	800,000
Patronage capital payable, noncurrent	$ 4,900,000	4,100,000
Hilcorp Alaska, LLC [Member]
Other Commitments [Line Items]
Commencement date of long term contract for purchase of gas supply	Jan. 01, 2015
Expiration date of long term contract for purchase of gas supply	Mar. 31, 2018
Hilcorp Alaska, LLC, Purchase Commitment Amendment 1 [Member]
Other Commitments [Line Items]
Commencement date of long term contract for purchase of gas supply	Sep. 15, 2014
Expiration date of long term contract for purchase of gas supply	Mar. 31, 2019
Percentage Of Met Natural Gas Needs	100.00%
Hilcorp Alaska, LLC, Purchase Commitment Amendment 2 [Member]
Other Commitments [Line Items]
Commencement date of long term contract for purchase of gas supply	Sep. 08, 2015
Expiration date of long term contract for purchase of gas supply	Mar. 31, 2023
Estimated amount of gas under contract | Mcf	60
Percentage Of Met Natural Gas Needs	100.00%
Marathon Alaska Production, LLC [Member]
Other Commitments [Line Items]
Commencement date of long term contract for purchase of gas supply	Apr. 01, 2011
Expiration date of long term contract for purchase of gas supply	Mar. 31, 2023
Estimated amount of gas under contract | Mcf	49
Percentage Of Met Natural Gas Needs	100.00%
Number of contract extensions | contract	2
Moving Overhead Lines Underground [Member]
Other Commitments [Line Items]
Other current liabilities	$ 4,206,223	$ 2,507,482
International Brotherhood of Electrical Workers [Member]
Other Commitments [Line Items]
Percentage of employees belonging to unions	70.00%
Number of collective bargaining agreements | item	3
Expiration date of collective bargaining agreements	Jun. 30, 2021
Hotel Employees and Restaurant Employees [Member]
Other Commitments [Line Items]
Number of collective bargaining agreements | item	1