v3.25.2
Short-Term Debt and Liquidity (Short-Term Debt Activity) (Details) - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Short-term Debt [Line Items]    
Average daily amount outstanding $ 975 $ 578
Weighted-average interest rate 4.61% 5.56%
Short-term Debt, Maximum Amount Outstanding During Period $ 1,603 $ 1,084
Peak interest rate 4.75% 5.68%
Parent Company    
Short-term Debt [Line Items]    
Average daily amount outstanding $ 659 $ 84
Weighted-average interest rate 4.63% 5.55%
Short-term Debt, Maximum Amount Outstanding During Period $ 1,139 $ 301
Peak interest rate 4.75% 5.60%
Union Electric Company    
Short-term Debt [Line Items]    
Average daily amount outstanding $ 226 $ 109
Weighted-average interest rate 4.60% 5.53%
Short-term Debt, Maximum Amount Outstanding During Period $ 650 $ 509
Peak interest rate 4.72% 5.68%
Ameren Illinois Company    
Short-term Debt [Line Items]    
Average daily amount outstanding $ 90 $ 385
Weighted-average interest rate 4.59% 5.57%
Short-term Debt, Maximum Amount Outstanding During Period $ 245 $ 694
Peak interest rate 4.70% 5.68%