Long-Term Debt And Equity Financings (Schedule Of Maturities Of Long-Term Debt) (Details) - USD ($)	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
2023	$ 340,000,000
2024	849,000,000
2025	300,000,000
2026	350,000,000
2027	950,000,000
Thereafter	11,358,000,000
Total	14,147,000,000
Ameren (parent)
Debt Instrument [Line Items]
2023	0
2024	450,000,000
2025	0
2026	350,000,000
2027	500,000,000
Thereafter	1,250,000,000
Total	2,550,000,000
Debt Instrument, Unamortized Discount or Premium and Debt Issuance Costs	14,000,000
Union Electric Company
Debt Instrument [Line Items]
2023	240,000,000
2024	350,000,000
2025	0
2026	0
2027	400,000,000
Thereafter	5,149,000,000
Total	6,139,000,000
Debt Instrument, Unamortized Discount or Premium and Debt Issuance Costs	53,000,000
Ameren Illinois Company
Debt Instrument [Line Items]
2023	100,000,000
2024	0
2025	300,000,000
2026	0
2027	0
Thereafter	4,488,000,000
Total	4,888,000,000
Debt Instrument, Unamortized Discount or Premium and Debt Issuance Costs	53,000,000
Ameren Transmission Company of Illinois
Debt Instrument [Line Items]
2023	0
2024	49,000,000
2025	0
2026	0
2027	50,000,000
Thereafter	471,000,000
Total	570,000,000
Debt Instrument, Unamortized Discount or Premium and Debt Issuance Costs	2,000,000
Unsecured Debt \| Ameren Transmission Company of Illinois \| Senior Unsecured Notes, 2.45% Due 2036
Debt Instrument [Line Items]
Debt instrument face amount	75,000,000	$ 75,000,000
Unsecured Debt \| Ameren Transmission Company of Illinois \| Senior Unsecured Notes, 2.45% Due 2036 \| Debt Instrument, Redemption, Period One
Debt Instrument [Line Items]
Thereafter	30,000,000
Unsecured Debt \| Ameren Transmission Company of Illinois \| Senior Unsecured Notes, 2.45% Due 2036 \| Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Thereafter	45,000,000
Unsecured Debt \| Ameren Transmission Company of Illinois \| Senior Unsecured Notes, 3.43%, Due 2050
Debt Instrument [Line Items]
2023	50,000,000
Debt instrument face amount	400,000,000	$ 450,000,000
Unsecured Debt \| Ameren Transmission Company of Illinois \| Senior Unsecured Notes, 3.43%, Due 2050 \| Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
2025	49,000,000
Unsecured Debt \| Ameren Transmission Company of Illinois \| Senior Unsecured Notes, 3.43%, Due 2050 \| Debt Instrument, Redemption, Period Three
Debt Instrument [Line Items]
Thereafter	50,000,000
Unsecured Debt \| Ameren Transmission Company of Illinois \| Senior Unsecured Notes, 3.43%, Due 2050 \| Debt Instrument, Redemption, Period Four
Debt Instrument [Line Items]
Thereafter	49,000,000
Unsecured Debt \| Ameren Transmission Company of Illinois \| Senior Unsecured Notes, 3.43%, Due 2050 \| Debt Instrument, Redemption, Period Five
Debt Instrument [Line Items]
Thereafter	50,000,000
Unsecured Debt \| Ameren Transmission Company of Illinois \| Senior Unsecured Notes, 3.43%, Due 2050 \| Debt Instrument, Redemption, Period Six
Debt Instrument [Line Items]
Thereafter	49,000,000
Unsecured Debt \| Ameren Transmission Company of Illinois \| Senior Unsecured Notes, 3.43%, Due 2050 \| Debt Instrument, Redemption, Period Seven
Debt Instrument [Line Items]
Thereafter	77,000,000
Unsecured Debt \| Ameren Transmission Company of Illinois \| Senior Unsecured Notes, 3.43%, Due 2050 \| Debt Instrument, Redemption, Period Eight
Debt Instrument [Line Items]
Thereafter	$ 76,000,000

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