Business Acquisitions (Details) (USD $)	3 Months Ended		9 Months Ended		0 Months Ended	3 Months Ended		9 Months Ended		15 Months Ended					9 Months Ended				15 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 MW D	Sep. 30, 2013	Jul. 01, 2014 Alaska Energy Resources Company [Member]	Sep. 30, 2014 Alaska Energy Resources Company [Member]	Sep. 30, 2013 Alaska Energy Resources Company [Member]	Sep. 30, 2014 Alaska Energy Resources Company [Member]	Sep. 30, 2013 Alaska Energy Resources Company [Member]	Sep. 30, 2014 Alaska Energy Resources Company [Member]	Jul. 01, 2014 Alaska Energy Resources Company [Member]	Sep. 30, 2014 Alaska Electric Light & Power [Member] employee	Jul. 01, 2014 Alaska Electric Light & Power [Member] employee	Dec. 31, 2013 Alaska Electric Light & Power [Member]	Sep. 30, 2014 Power purchase agreement [Member] Alaska Electric Light & Power [Member] MW	Sep. 30, 2014 Hydroelectric Production [Member] Alaska Electric Light & Power [Member] MW	Sep. 30, 2014 Fossil Fuel Plant [Member] Alaska Electric Light & Power [Member] MW	Sep. 30, 2014 AEL&P Hydroelectric Production [Member] Alaska Electric Light & Power [Member] MW generating_facilities	Sep. 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	$ 301,558,000	$ 289,477,000	$ 1,060,716,000	$ 1,037,464,000		$ 9,224,000	$ 9,309,000	$ 35,319,000	$ 31,243,000
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					4,500,014
Business Combination Equity Consideration Share Price											$ 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
Business Combination, Acquisition Related Costs										2,900,000									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