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Supplemental Information (Supplemental Cash Flow Information) (Details) - USD ($) $ in Millions | 9 Months Ended
--- | ---
Sep. 30, 2023 | Sep. 30, 2022
Supplemental Cash Flow Information [Line Items] |  |
Accrued capital expenditures, including nuclear fuel expenditures | $ 518 | $ 367
Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund | 66 | (262)
Return on investment in industrial development revenue bonds | 240 | 0
Termination of a financing obligation | 240 | 0
Issuance of common stock for stock-based compensation |  |
Supplemental Cash Flow Information [Line Items] |  |
Stock Issued | 37 | 31
Issuance of common stock under the DRPlus |  |
Supplemental Cash Flow Information [Line Items] |  |
Stock Issued | 7 | 8
Union Electric Company |  |
Supplemental Cash Flow Information [Line Items] |  |
Accrued capital expenditures, including nuclear fuel expenditures | 246 | 187
Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund | 66 | (262)
Return on investment in industrial development revenue bonds | 240 | 0
Termination of a financing obligation | 240 | 0
Union Electric Company | Issuance of common stock for stock-based compensation |  |
Supplemental Cash Flow Information [Line Items] |  |
Stock Issued | 0 | 0
Union Electric Company | Issuance of common stock under the DRPlus |  |
Supplemental Cash Flow Information [Line Items] |  |
Stock Issued | 0 | 0
Ameren Illinois Company |  |
Supplemental Cash Flow Information [Line Items] |  |
Accrued capital expenditures, including nuclear fuel expenditures | 237 | 180
Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund | 0 | 0
Return on investment in industrial development revenue bonds | 0 | 0
Termination of a financing obligation | 0 | 0
Ameren Illinois Company | Issuance of common stock for stock-based compensation |  |
Supplemental Cash Flow Information [Line Items] |  |
Stock Issued | 0 | 0
Ameren Illinois Company | Issuance of common stock under the DRPlus |  |
Supplemental Cash Flow Information [Line Items] |  |
Stock Issued | $ 0 | $ 0

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