Short-Term Debt And Liquidity (Narrative) (Details) (USD $)									12 Months Ended			12 Months Ended
	Nov. 14, 2012 Illinois Credit Agreement 2012	Dec. 31, 2013 Illinois Credit Agreement 2012 Maximum	Dec. 31, 2013 Illinois Credit Agreement 2012 Ameren Illinois Company	Nov. 14, 2012 Missouri Credit Agreement 2012	Dec. 31, 2013 Missouri Credit Agreement 2012 Maximum	Dec. 31, 2013 Missouri Credit Agreement 2012 Union Electric Company	Dec. 31, 2013 Credit Agreements 2012	Dec. 31, 2013 Unilateral Borrowing Agreement Ameren Illinois Company	Dec. 31, 2013 Multiyear Credit Facility lender	Dec. 31, 2013 Multiyear Credit Facility Maximum	Dec. 31, 2013 Commercial Paper	Dec. 31, 2013 Utilities	Dec. 31, 2012 Utilities
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1,100,000,000.0	$ 1,300,000,000.0	$ 800,000,000	$ 1,000,000,000	$ 1,200,000,000.0	$ 800,000,000	$ 1,700,000,000.0	$ 500,000,000	$ 2,100,000,000.0
Number of lenders									24
Line of credit facility, maximum borrowing capacity, per lender									125,000,000
Commercial paper maximum issuance											500,000,000
Actual debt-to-capital ratio			0.44			0.47			0.48	0.65
Minimum ratio of consolidated funds from operations plus interest expense to consolidated interest expense as of balance sheet date									2.0 to 1.0
Current ratio of consolidated funds from operations plus interest expense to consolidated interest expense as of balance sheet date									5.3 to 1.0
Covenant terms, default provisions, maximum indebtedness							$ 50,000,000
Short Term Debt, Weighted Average Interest Rate During Period												0.14%	0.13%
Letters of credit portion of aggregate commitment									25.00%