Related Party Transactions (Notes Receivable From Related Party) (Details) (Midwest Generation LLC [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Midwest Generation LLC [Member]
Related Party Transaction [Line Items]
Due from affiliates, gross	$ 19	$ 12
Due from affiliates, valuation allowance	(19)	(12)
Due from affiliates, carrying value	0	0
Interest receivable from affiliate, gross	55	55
Interest receivable from affiliate, valuation allowance	(55)	(55)
Interest receivable from affiliate, carrying value	0	0
Notes receivable from affiliate, gross	1,304	1,311
Notes receivable from affiliate, valuation allowance	(1,304)	(1,311)
Notes receivable from affiliate, carrying value	0	0
Total due from affiliates, gross	1,378	1,378
Total due from affiliates, valuation allowance	(1,378)	(1,378)
Total due from affiliates, carrying amount	$ 0	$ 0