Utility Plant (Details) - USD ($)		Dec. 31, 2017	Dec. 31, 2016
Public Utility, Property, Plant and Equipment [Line Items]
Other property, plant and equipment		$ 1,205,092,224	$ 1,192,513,869
Electric plant in service		1,205,092,224	1,192,513,869
Construction work in progress		17,952,573	18,455,940
Total utility plant		1,223,044,797	1,210,969,809
Steam Production Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Generation and processing		101,116,277	101,116,277
Hydroelectric Production Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Generation and processing		33,659,129	33,659,129
Other Production Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Generation and processing		287,765,474	287,404,484
Transmission Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Transmission		296,018,078	282,040,969
Distribution Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Distribution		315,862,812	294,641,485
General Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Other property, plant and equipment		55,164,994	54,982,432
Electric plant in service		55,164,994	54,982,432
Unclassified Electric Plant In Service [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Other property, plant and equipment	[1]	60,294,349	83,457,981
Electric plant in service	[1]	60,294,349	83,457,981
Intangible Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Transmission	[1]	5,455,371	5,455,371
Beluga River Unit [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Other property, plant and equipment		47,927,331	47,927,331
Electric plant in service		47,927,331	47,927,331
Other [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Other- land	[1]	$ 1,828,409	$ 1,828,409

[1] Unclassified electric plant in service consists of complete unclassified general plant, generation plant, transmission plant and distribution plant. Depreciation of unclassified electric plant in service has been included in functional plant depreciation accounts in accordance with the anticipated eventual classification of the plant investment. Intangible plant represents Chugach's share of a Bradley Lake transmission line financed internally. Other represents Electric Plant Held for Future Use.