Long-Term Debt And Equity Financings (Schedule Of Average Interest Rates) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
1992 Series due 2022 | Union Electric Company
Debt Instrument [Line Items]
Debt instrument, interest rate during period	0.66%	0.06%
1998 Series A due 2033 | Union Electric Company
Debt Instrument [Line Items]
Debt instrument, interest rate during period	0.91%	0.24%
1998 Series B due 2033 | Union Electric Company
Debt Instrument [Line Items]
Debt instrument, interest rate during period	0.92%	0.24%
1998 Series C due 2033 | Union Electric Company
Debt Instrument [Line Items]
Debt instrument, interest rate during period	0.97%	0.24%
Series B-1 1993 Due 2028 | Ameren Illinois Company
Debt Instrument [Line Items]
Debt instrument, interest rate during period	0.70%	0.49%