Schedule I - Condensed Financial Information Of Parent (Impairment and Other Charges) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended		1 Months Ended
	Dec. 31, 2013 Parent Company Merchant Generation	Dec. 31, 2012 Parent Company Merchant Generation	Jan. 31, 2014 New Ameren Energy Resources Company, LLC
Impairment and Other Charges [Line Items]
Impairment charge on long-lived assets and related charges	$ 201	$ 1,880
Disposal Group, Including Discontinued Operation, Working Capital Adjustment, Period			120 days