Short-Term Debt And Liquidity (Commercial Paper) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Short-term Debt [Line Items]
Average daily amount outstanding	$ 852	$ 604
Commercial paper issuances outstanding at period-end	$ 1,070	$ 545
Weighted-average interest rate	2.28%	0.22%
Peak amount outstanding during period(a)	$ 1,267	$ 1,134
Peak interest rate	4.95%	0.38%
Parent Company
Short-term Debt [Line Items]
Average daily amount outstanding	$ 485	$ 387
Commercial paper issuances outstanding at period-end	$ 477	$ 277
Weighted-average interest rate	2.41%	0.22%
Peak amount outstanding during period(a)	$ 718	$ 650
Peak interest rate	4.80%	0.38%
Union Electric Company
Short-term Debt [Line Items]
Average daily amount outstanding	$ 229	$ 99
Commercial paper issuances outstanding at period-end	$ 329	$ 165
Weighted-average interest rate	1.71%	0.22%
Peak amount outstanding during period(a)	$ 539	$ 546
Peak interest rate	4.95%	0.35%
Ameren Illinois Company
Short-term Debt [Line Items]
Average daily amount outstanding	$ 138	$ 118
Commercial paper issuances outstanding at period-end	$ 264	$ 103
Weighted-average interest rate	2.79%	0.21%
Peak amount outstanding during period(a)	$ 404	$ 485
Peak interest rate	4.80%	0.35%