Patronage Capital (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Patronage Capital [Line Items]
Patronage capital	$ 172,928,887	$ 169,996,436
Patronage capital assigned	166,880,163	164,182,580
Patronage capital to be assigned to members	6,048,724	5,813,856
Patronage capital payable, noncurrent	8,798,077	12,008,499
Retirement of capital credits	3,116,273	3,265,201	$ 3,190,124
Excluding Homer Electric Association Retirement [Member]
Patronage Capital [Line Items]
Retirement of capital credits	2,631,928	3,001,426	3,007,772
Excluding Matanuska Electric Association And Homer Electric Association Patronage Capital [Member]
Patronage Capital [Line Items]
Patronage capital payable, current	$ 57,036	2,014,080	$ 2,105,440
Assignable Margins [Member]
Patronage Capital [Line Items]
Secured debt covenant restriction during period	50.00%
Homer Electric Association, Inc. [Member]
Patronage Capital [Line Items]
Return of patronage capital term after expiration date of Power Sales Agreement	5 years
Expiration date of power sales agreement	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]
Patronage Capital [Line Items]
Payments to retire patronage capital	800,000
Patronage capital payable, noncurrent	$ 4,900,000	$ 4,100,000
Minimum [Member] | Aggregate Equities And Margins To Total Liabilities And Equities And Margins [Member]
Patronage Capital [Line Items]
Secured debt covenant restriction during period	30.00%
Patronage Capital [Member]
Patronage Capital [Line Items]
Secured debt covenant restriction at period end	5.00%