Risk Management and Derivative Financial Instruments (Details 3) (Electric)	6 Months Ended
	Jun. 30, 2012 Dth PerDth
Natural Gas Usage - Remainder 2012
Volumes and percentage of anticipated volume of natural gas usage
% Hedged (as a percent)	73.00%
Physical	1,640,000
Financial	1,110,000
Average Price (in dollars per dth)	6.311
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged (as a percent)	73.00%
Natural Gas Usage - 2013
Volumes and percentage of anticipated volume of natural gas usage
% Hedged (as a percent)	52.00%
Physical	2,020,000
Financial	2,140,000
Average Price (in dollars per dth)	5.624
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged (as a percent)	52.00%
Natural Gas Usage - 2014
Volumes and percentage of anticipated volume of natural gas usage
% Hedged (as a percent)	29.00%
Physical	460,000
Financial	2,040,000
Average Price (in dollars per dth)	5.041
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged (as a percent)	29.00%
Natural Gas Usage - 2015
Volumes and percentage of anticipated volume of natural gas usage
% Hedged (as a percent)	15.00%
Financial	1,410,000
Average Price (in dollars per dth)	5.031
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged (as a percent)	15.00%
Natural Gas Usage - 2016
Volumes and percentage of anticipated volume of natural gas usage
% Hedged (as a percent)	4.00%
Financial	400,000
Average Price (in dollars per dth)	4.185
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged (as a percent)	4.00%
Current Year Procurement Guidelines
Volumes and percentage of anticipated volume of natural gas usage
% Hedged (as a percent)	100.00%
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%
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged (as a percent)	100.00%
First Year Procurement Guidelines
Volumes and percentage of anticipated volume of natural gas usage
% Hedged (as a percent)	60.00%
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged (as a percent)	60.00%
Second Year Procurement Guidelines
Volumes and percentage of anticipated volume of natural gas usage
% Hedged (as a percent)	40.00%
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged (as a percent)	40.00%
Third Year Procurement Guidelines
Volumes and percentage of anticipated volume of natural gas usage
% Hedged (as a percent)	20.00%
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged (as a percent)	20.00%
Fourth Year Procurement Guidelines
Volumes and percentage of anticipated volume of natural gas usage
% Hedged (as a percent)	10.00%
Minimum Percentage Hedged for Electric Segment
End of Year Minimum % Hedged (as a percent)	10.00%