Long-Term Debt And Equity Financings (Schedule Of Average Interest Rates) (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
1992 Series due 2022 | Union Electric Company
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period	2.58%	2.37%
1998 Series A due 2033 | Union Electric Company
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period	3.43%	2.76%
1998 Series B due 2033 | Union Electric Company
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period	3.57%	2.79%
1998 Series C due 2033 | Union Electric Company
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period	3.43%	2.83%
Series B-1 1993 Due 2028 | Ameren Illinois Company
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period	1.68%	1.58%