Business Acquisitions (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended		6 Months Ended				0 Months Ended		12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 D MW	Jun. 30, 2013	Jun. 30, 2014 Alaska Energy Resources Company [Member]	Jun. 30, 2013 Alaska Energy Resources Company [Member]	Jun. 30, 2014 Alaska Energy Resources Company [Member]	Jun. 30, 2013 Alaska Energy Resources Company [Member]	Jun. 30, 2014 Alaska Energy Resources Company [Member]	Dec. 31, 2013 Alaska Electric Light & Power [Member] employee	Jun. 30, 2014 Power purchase agreement [Member] Alaska Electric Light & Power [Member] MW	Jun. 30, 2014 Hydroelectric Production [Member] Alaska Electric Light & Power [Member] MW	Jun. 30, 2014 Fossil Fuel Plant [Member] Alaska Electric Light & Power [Member] MW	Jun. 30, 2014 AEL&P Hydroelectric Production [Member] Alaska Electric Light & Power [Member] MW generating_facilities	Jul. 01, 2014 Subsequent Event [Member] Alaska Energy Resources Company [Member]	Jul. 01, 2014 Subsequent Event [Member] Alaska Energy Resources Company [Member]	Jun. 30, 2014 Acquisition-related Costs [Member] Alaska Energy Resources Company [Member]
Business Acquisition [Line Items]
Number of Electric Generating Facilities														4
Business Acquisition, Share Price																$ 33.35
Number of Customers										16,000
Operating revenues	$ 312,580,000	$ 307,488,000	$ 759,158,000	$ 747,987,000	$ 11,782,000	$ 10,651,000	$ 24,546,000	$ 23,303,000
Total Rate Base										109,000,000
Entity Number of Employees										60
Peak electric usage			68
Evaluated Power Capacity											78	102.7	93.9	24.7
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares															4.5
Business Combination Equity Consideration Share Price					$ 32.46		$ 32.46		$ 32.46
Business Combination Number of Trading Days to Price Equity Consideration Share Price			10
Merger Consideration - Total																170,000,000
Representative Reimbursement Amount			4,697,000	0			4,697,000
Business Combination, Acquisition Related Costs									2,300,000								400,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents																(19,704,000)
Business Acquisition Recognized Identifiable Assets Acquired and Liabilities Assumed Current and Long-Term Debt																38,832,000
Business Acquisition Contract Price Closing Adjustments																(104,000)
Business Acquisition Adjusted Contract Price																150,768,000
Business Combination, Consideration Transferred															$ 154,772,000