Summary of Significant Accounting Policies (Income Taxes and Tax-Allocation Agreements) (Details) (USD $)			1 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Feb. 28, 2014 Subsequent Event	Dec. 31, 2013 Subsequent Event	Dec. 31, 2013 Midwest Generation LLC [Member]	Dec. 31, 2012 Midwest Generation LLC [Member]
Restructuring Cost and Reserve [Line Items]
Tax attributes estimated amount			$ 1,190,000,000
Liabilities assumed, net			241,000,000
Percentage of tax benefits to be paid			50.00%
Cash portion of settlement payment				225,000,000
Related Party Transaction, Rate				5.00%
Deferred Tax Assets, Valuation Allowance	752,000,000	444,000,000			767,000,000	533,000,000
EIX Estimated Liabilities Assumed			$ 350,000,000