Long-Term Debt And Equity Financings (Schedule Of Average Interest Rates) (Details)	12 Months Ended
	Dec. 31, 2013 1992 Series due 2022 Union Electric Company	Dec. 31, 2012 1992 Series due 2022 Union Electric Company	Dec. 31, 2013 1998 Series A due 2033 Union Electric Company	Dec. 31, 2012 1998 Series A due 2033 Union Electric Company	Dec. 31, 2013 1998 Series B due 2033 Union Electric Company	Dec. 31, 2012 1998 Series B due 2033 Union Electric Company	Dec. 31, 2013 1998 Series C due 2033 Union Electric Company	Dec. 31, 2012 1998 Series C due 2033 Union Electric Company	Dec. 31, 2013 Series B-1 1993 Due 2028 Ameren Illinois Company	Dec. 31, 2012 Series B-1 1993 Due 2028 Ameren Illinois Company	Dec. 31, 2013 Secured Debt 3.90% Senior secured notes due 2042 Union Electric Company	Sep. 20, 2012 Secured Debt 3.90% Senior secured notes due 2042 Union Electric Company	Sep. 11, 2012 Secured Debt 3.90% Senior secured notes due 2042 Union Electric Company
Debt Instrument [Line Items]
Long-term debt interest rate											3.90%	3.90%	3.90%
Debt instrument, interest rate during period	0.17%	0.30%	0.34%	0.65%	0.33%	0.64%	0.34%	0.64%	0.14%	0.22%