Business Acquisitions Assets Acquired Liabilities Assumed (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jul. 01, 2014 Subsequent Event [Member] Alaska Energy Resources Company [Member]	Jun. 30, 2014 AEL&P Hydroelectric Production [Member] Alaska Electric Light & Power [Member] generating_facilities
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents			$ 19,704
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables			3,851
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables			77
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory			2,017
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other			999
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets			26,571
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Public Utilities Property Plant and Equipment Plant in Service			113,964
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed Capital Lease Assets			71,007
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Public Utilities Property Plant and Equipment, Construction Work in Progress			3,440
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment			188,411
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Noncurrent Non-Utility Property			6,660
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed Electric Plant Held for Future Use			3,711
Goodwill	5,246	76,257	50,629
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets			5,368
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other			13,137
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Assets			66,368
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets			281,350
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable			700
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Long-term Debt			3,773
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other			2,901
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities			7,374
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt			37,227
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Capital Lease Obligation			68,840
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities			126,578
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net			$ 154,772
Number of Electric Generating Facilities				4