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Rate And Regulatory Matters (Schedule Of Regulatory Assets And Liabilities) (Details) - USD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Feb. 28, 2021
Regulatory assets: |  |  |
Total regulatory assets | $ 2,175 | $ 1,780 |
Less: current regulatory assets | (365) | (354) |
Noncurrent regulatory assets | 1,810 | 1,426 |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 5,599 | 5,445 |
Less: current regulatory liabilities | (87) | (136) |
Noncurrent regulatory liabilities | 5,512 | 5,309 |
Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 856 | 848 |
Less: current regulatory assets | (101) | (254) |
Noncurrent regulatory assets | 755 | 594 |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 2,974 | 2,941 |
Less: current regulatory liabilities | (15) | (70) |
Noncurrent regulatory liabilities | $ 2,959 | 2,871 |
PISA deferral percentage | 85.00% |  |
Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | $ 1,287 | 908 |
Less: current regulatory assets | (252) | (87) |
Noncurrent regulatory assets | 1,035 | 821 |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 2,489 | 2,377 |
Less: current regulatory liabilities | (71) | (64) |
Noncurrent regulatory liabilities | 2,418 | 2,313 |
Under-recovered FAC |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 72 | 140 |
Under-recovered FAC | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 72 | 140 |
Under-recovered FAC | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 0 | 0 |
Under-recovered Illinois electric power costs |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 10 | 33 |
Under-recovered Illinois electric power costs | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 0 | 0 |
Under-recovered Illinois electric power costs | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 10 | 33 |
Under-recovered PGA |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 6 | 23 |
Under-recovered PGA | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 6 | 23 | $ 53
Under-recovered PGA | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 0 | 0 |
MTM derivative losses |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 168 | 136 |
MTM derivative losses | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 25 | 68 |
MTM derivative losses | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 143 | 68 |
IEIMA revenue requirement reconciliation adjustment |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 239 | 134 |
IEIMA revenue requirement reconciliation adjustment | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 0 | 0 |
IEIMA revenue requirement reconciliation adjustment | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | $ 239 | 134 |
Regulatory liabilities: |  |  |
Regulatory asset, amortization period | 2 years |  |
FERC revenue requirement reconciliation adjustment |  |  |
Regulatory assets: |  |  |
Total regulatory assets | $ 54 | 33 |
Regulatory liabilities: |  |  |
Regulatory asset, amortization period | 2 years |  |
FERC revenue requirement reconciliation adjustment | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | $ 0 | 0 |
FERC revenue requirement reconciliation adjustment | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 25 | 11 |
Under-recovered VBA |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 49 | 0 |
Under-recovered VBA | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 0 | 0 |
Under-recovered VBA | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 49 | 0 |
Income taxes |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 207 | 185 |
Regulatory liabilities: |  |  |
Total regulatory liabilities | $ 1,809 | 1,931 |
Weighted-average amortization period | 36 years |  |
Income taxes | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | $ 126 | 111 |
Regulatory liabilities: |  |  |
Total regulatory liabilities | $ 999 | 1,095 |
Weighted-average amortization period | 28 years |  |
Income taxes | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | $ 78 | 72 |
Regulatory liabilities: |  |  |
Total regulatory liabilities | $ 724 | 749 |
Weighted-average amortization period | 43 years |  |
Bad debt rider |  |  |
Regulatory assets: |  |  |
Total regulatory assets | $ 43 | 5 |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 7 | 21 |
Bad debt rider | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 0 | 0 |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 0 | 0 |
Bad debt rider | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 43 | 5 |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 7 | 21 |
Callaway refueling and maintenance outage costs |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 37 | 33 |
Callaway refueling and maintenance outage costs | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | $ 37 | 33 |
Regulatory liabilities: |  |  |
Regulatory asset, amortization period | 18 months |  |
Callaway refueling and maintenance outage costs | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | $ 0 | 0 |
Unamortized loss on reacquired debt |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 50 | 54 |
Unamortized loss on reacquired debt | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 45 | 47 |
Unamortized loss on reacquired debt | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 5 | 7 |
Environmental cost riders |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 50 | 64 |
Environmental cost riders | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 0 | 0 |
Environmental cost riders | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 50 | 64 |
Storm costs |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 27 | 14 |
Storm costs | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 0 | 0 |
Storm costs | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 27 | 14 |
Allowance for funds used during construction for pollution control equipment |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 10 | 11 |
Allowance for funds used during construction for pollution control equipment | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 10 | 11 |
Allowance for funds used during construction for pollution control equipment | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 0 | 0 |
Customer generation rebate program |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 54 | 50 |
Customer generation rebate program | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 0 | 0 |
Customer generation rebate program | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 54 | 50 |
PISA |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 386 | 320 |
PISA | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | $ 386 | 320 |
Regulatory liabilities: |  |  |
Regulatory asset, amortization period | 20 years |  |
PISA | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | $ 0 | 0 |
RESRAM |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 48 | 6 |
RESRAM | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 48 | 6 |
RESRAM | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 0 | 0 |
Certain Meramec Energy Center costs |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 39 | 51 |
Certain Meramec Energy Center costs | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | $ 39 | 51 |
Regulatory liabilities: |  |  |
Regulatory asset, amortization period | 5 years |  |
Certain Meramec Energy Center costs | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | $ 0 | 0 |
FEJA energy-efficiency rider |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 500 | 416 |
FEJA energy-efficiency rider | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 0 | 0 |
FEJA energy-efficiency rider | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 500 | 416 |
Property Tax Tracker |  |  |
Regulatory assets: |  |  |
Total regulatory assets | $ 13 | 3 |
Regulatory liabilities: |  |  |
Regulatory asset, amortization period | 2 years |  |
Property Tax Tracker | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | $ 13 | 3 |
Property Tax Tracker | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 0 | 0 |
Other regulatory assets |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 113 | 69 |
Other regulatory assets | Ameren Missouri |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 49 | 35 |
Other regulatory assets | Ameren Illinois |  |  |
Regulatory assets: |  |  |
Total regulatory assets | 64 | 34 |
Over-recovered Illinois electric power costs |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 36 | 0 |
Over-recovered Illinois electric power costs | Ameren Missouri |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 0 | 0 |
Over-recovered Illinois electric power costs | Ameren Illinois |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | $ 36 | 0 |
Amortization period | 1 year |  |
Over-recovered PGA |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | $ 40 | 10 |
Over-recovered PGA | Ameren Missouri |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 7 | 0 |
Over-recovered PGA | Ameren Illinois |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 33 | 10 |
MTM derivative gains |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 22 | 91 |
MTM derivative gains | Ameren Missouri |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 19 | 51 |
MTM derivative gains | Ameren Illinois |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 3 | 40 |
Cost of removal |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 2,186 | 2,091 |
Cost of removal | Ameren Missouri |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 1,098 | 1,064 |
Cost of removal | Ameren Illinois |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 1,038 | 989 |
AROs |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 524 | 365 |
AROs | Ameren Missouri |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 524 | 365 |
AROs | Ameren Illinois |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 0 | 0 |
Pension and postretirement benefit costs |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 346 | 404 |
Pension and postretirement benefit costs | Ameren Missouri |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 202 | 242 |
Pension and postretirement benefit costs | Ameren Illinois |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 144 | 162 |
Pension and postretirement benefit costs tracker |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 111 | 60 |
Pension and postretirement benefit costs tracker | Ameren Missouri |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | $ 111 | 60 |
Regulatory liability, amortization period | 3 years |  |
Pension and postretirement benefit costs tracker | Ameren Illinois |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | $ 0 | 0 |
Renewable energy credits and zero emission credits |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 489 | 373 |
Renewable energy credits and zero emission credits | Ameren Missouri |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 0 | 0 |
Renewable energy credits and zero emission credits | Ameren Illinois |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 489 | 373 |
Other regulatory liabilities |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 29 | 99 |
Other regulatory liabilities | Ameren Missouri |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | 14 | 64 |
Other regulatory liabilities | Ameren Illinois |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | $ 15 | 33 |
FAC adjustments | Ameren Missouri |  |  |
Regulatory liabilities: |  |  |
Accumulation period | 4 months |  |
Regulatory asset, amortization period | 8 months |  |
Asset Retirement Obligation - Nuclear decommissioning trust fund balance | Ameren Missouri |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | $ 1,150 | 958 |
Asset Retirement Obligation - removal costs | Ameren Missouri |  |  |
Regulatory liabilities: |  |  |
Total regulatory liabilities | $ 626 | $ 593 |
Minimum | Under-recovered PGA | Ameren Missouri |  |  |
Regulatory liabilities: |  |  |
Regulatory asset, amortization period | 12 months |  |
Minimum | FEJA energy-efficiency rider | Ameren Illinois |  |  |
Regulatory liabilities: |  |  |
Regulatory asset, amortization period | 3 years |  |
Maximum | Under-recovered PGA | Ameren Missouri |  |  |
Regulatory liabilities: |  |  |
Regulatory asset, amortization period | 36 months |  |
Maximum | FEJA energy-efficiency rider | Ameren Illinois |  |  |
Regulatory liabilities: |  |  |
Regulatory asset, amortization period | 12 years |  |

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