Beluga River Unit (Narrative) (Details)		3 Months Ended		9 Months Ended
	Feb. 04, 2016 USD ($) a	Sep. 30, 2016 USD ($) MMcf	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) mi MMcf	Sep. 30, 2015 USD ($)	Apr. 22, 2016 MMcf
Business Acquisition [Line Items]
Revenue		$ 45,132,973	$ 43,109,512	$ 140,005,625	$ 165,780,449
Beluga River Unit [Member]
Business Acquisition [Line Items]
Date of Purchase and Sale Agreement				Feb. 04, 2016
Total purchase price	$ 148,000,000
Cash consideration		$ 44,403,922		$ 44,403,922
Working interest ownership percentage	30.00%	10.00%		10.00%
Number of lease acres | a	15,500
Number of lease acres in Unit / Participating Area | a	8,200
Number of lease acres held by Unit | a	7,300
Closing date of Purchase and Sale Agreement				Apr. 22, 2016
Number of miles from Anchorage | mi				35
Acquisition costs		$ 1,400,000		$ 1,400,000
Amount of gas acquired | MMcf		68,354		68,354		69,099
Expiration date of gas sales				Dec. 31, 2017
Revenue				$ 1,800,000
Lifted amount of gas in proven developed reserves | MMcf		1,300		1,300
Remaining amount of gas in proven developed reserves | MMcf		25,700		25,700
Municipal Light & Power [Member] | Beluga River Unit [Member]
Business Acquisition [Line Items]
Working interest ownership percentage	70.00%	56.70%		56.70%		33.30%
ConocoPhillips (COP) [Member] | Beluga River Unit [Member]
Business Acquisition [Line Items]
Working interest ownership percentage						33.30%
ConocoPhillips (COP) [Member] | Deep Oil Resources [Member]
Business Acquisition [Line Items]
Working interest ownership percentage	67.00%
Hilcorp Alaska, LLC [Member] | Beluga River Unit [Member]
Business Acquisition [Line Items]
Working interest ownership percentage		33.30%		33.30%		33.30%
Minimum [Member] | Beluga River Unit [Member]
Business Acquisition [Line Items]
Effective annual cost savings				$ (2,000,000)
Maximum [Member] | Beluga River Unit [Member]
Business Acquisition [Line Items]
Effective annual cost savings				$ (3,000,000)
ENSTAR [Member] | ConocoPhillips (COP) [Member]
Business Acquisition [Line Items]
Expiration year of Gas Sale and Purchase Agreement				2017