Hydro Transaction Hydro-electric (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended			3 Months Ended
	Sep. 30, 2014	Sep. 26, 2013 days watts	Sep. 26, 2013 Kerr Project [Member] watts	Dec. 31, 2014 Scenario, Forecast [Member]
Significant Acquisitions and Disposals [Line Items]
Megawatts of hydro-electric generation capacity		633	194
Purchase price		$ 900	$ 30
Owned average load serving requirement	60.00%
Estimated rate base, Hydro Electric	870
Authorized return on equity	9.80%
Hydro assets, useful life	50 years
Authorized cost of debt	4.25%
Capital structure, percentage of debt	52.00%
Capitalized structure, percentage of equity	48.00%
Annual revenue requirement increase	117
Debt instrument, term	30 years
Long term debt, Hydro financing	27.0			450.0
Common stock, aggregate gross sales price				400
Estimated cash from operating activities				50
Bridge term loan facility		900
Bridge term loan facility agreement term		364
Estimated conveyance price of hydro facility			18.3
Estimated reference price less conveyance price			11.7
Authorized issuance of securities		900
Transaction costs	2.3
Debt related commitment fees and debt issuance costs	$ 5.6