Risk Management and Derivative Financial Instruments (Details 3) (Electric)	3 Months Ended
	Mar. 31, 2013 Dth
Natural Gas Usage - Remainder 2013
Volumes and percentage of anticipated volume of natural gas usage
% Hedged	60.00%
Physical	1,630,000
Financial	3,050,000
Average Price (in dollars per dth)	5.146
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged	60.00%
Natural Gas Usage - 2014
Volumes and percentage of anticipated volume of natural gas usage
% Hedged	39.00%
Physical	460,000
Financial	3,540,000
Average Price (in dollars per dth)	4.741
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged	39.00%
Natural Gas Usage - 2015
Volumes and percentage of anticipated volume of natural gas usage
% Hedged	20.00%
Financial	1,910,000
Average Price (in dollars per dth)	4.928
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged	20.00%
Natural Gas Usage - 2016
Volumes and percentage of anticipated volume of natural gas usage
% Hedged	10.00%
Financial	1,000,000
Average Price (in dollars per dth)	4.410
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged	10.00%
Current Year Procurement Guidelines
Procurement guidelines
Maximum flexibility to hedge any future year's expected requirements (as a percent)	80.00%
Maximum percentage of volume to be hedged in any given month	100.00%
First Year Procurement Guidelines
Volumes and percentage of anticipated volume of natural gas usage
% Hedged	60.00%
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged	60.00%
Second Year Procurement Guidelines
Volumes and percentage of anticipated volume of natural gas usage
% Hedged	40.00%
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged	40.00%
Third Year Procurement Guidelines
Volumes and percentage of anticipated volume of natural gas usage
% Hedged	20.00%
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged	20.00%
Fourth Year Procurement Guidelines
Volumes and percentage of anticipated volume of natural gas usage
% Hedged	10.00%
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged	10.00%
Maximum | Current Year Procurement Guidelines
Volumes and percentage of anticipated volume of natural gas usage
% Hedged	100.00%
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged	100.00%