Regulatory Matters (Details) Mcf in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($) Mcf	Jun. 30, 2017	Sep. 30, 2017 USD ($) $ / Mcfe Mcf	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Other Commitments [Line Items]
Proposed increase (decrease) in rates				$ (5,900,000)
Approved percentage increase (decrease) in rates	1.90%
Other assets, noncurrent, deferred charges, net	$ 33,819,717		$ 33,819,717		$ 25,140,957
Beluga Power Plant [Member]
Other Commitments [Line Items]
Other assets, noncurrent, deferred charges, net	11,400,000		$ 11,400,000
Beluga Power Plant, Unit 1 [Member] | Beluga Power Plant [Member]
Other Commitments [Line Items]
Amortization period of regulatory asset			30 months
Other assets, noncurrent, deferred charges, net	300,000		$ 300,000
Beluga Power Plant, Unit 2 [Member] | Beluga Power Plant [Member]
Other Commitments [Line Items]
Amortization period of regulatory asset			108 months
Other assets, noncurrent, deferred charges, net	$ 11,100,000		$ 11,100,000
City Of Seward [Member]
Other Commitments [Line Items]
Proposed percentage increase (decrease) in rates				(4.60%)
Approved percentage increase (decrease) in rates		(4.90%)
City Of Seward [Member] | Total Customer Bill Basis [Member]
Other Commitments [Line Items]
Proposed percentage increase (decrease) in rates				(1.90%)
Retail Customers [Member]
Other Commitments [Line Items]
Proposed percentage increase (decrease) in rates				(4.70%)
Approved percentage increase (decrease) in rates		(3.00%)
Retail Customers [Member] | Total Customer Bill Basis [Member]
Other Commitments [Line Items]
Proposed percentage increase (decrease) in rates				(3.20%)
Furie Operating Alaska, LLC Purchase Commitment [Member]
Other Commitments [Line Items]
Term of purchase commitment			16 years
Commencement date of long term contract for purchase of gas supply			Apr. 01, 2023
Expiration date of long term contract for purchase of gas supply			Mar. 31, 2033
Approximate annual volume | Mcf	1.8		1.8
Furie Operating Alaska, LLC Purchase Commitment [Member] | Minimum [Member]
Other Commitments [Line Items]
Percentage of met natural gas needs			20.00%
Price per Mcf | $ / Mcfe			7.16
Furie Operating Alaska, LLC Purchase Commitment [Member] | Maximum [Member]
Other Commitments [Line Items]
Percentage of met natural gas needs			25.00%
Price per Mcf | $ / Mcfe			7.98