Regulatory Matters (Details Textuals) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
Regulatory Liabilities [Line Items]
Accrued Liabilities for RDM Refunds Relating to 2010	$ 56
Accrued Liabilities for RDM Refunds Relating to 2011	71
Approved Rate Base Relating to the AMI Program	37
Expenditures Net of Grant Funds for AMI Program	90
Matching Grant Funds for the AMI Program	58
RDM Refund Range Minimum First Pilot	56
RDM Refund Range Maximum First Pilot	140
RDM Refund Range Minimum Second Pilot	10
RDM Refund Range Maximum Second Pilot	130
Requested Recovery of Enery Optimization Expenses for Future Period	294
EO Plan Expense Cummulative Over Recovery	23
Vulnerable household warmth fund amount to be collected	48
Customer Monthly Credits to Remove Annualized Funding for VHWF from Rates	$ 40