XML 119 R53.htm IDEA: XBRL DOCUMENT v3.20.4
Property and Plant, Net (Schedule of Capitalized Software, Future Amortization Expense) (Details) - Capitalized software costs
$ in Millions
Dec. 31, 2020
USD ($)
Finite-Lived Intangible Assets [Line Items]  
2021 $ 105
2022 94
2023 81
2024 55
2025 23
Union Electric Company  
Finite-Lived Intangible Assets [Line Items]  
2021 55
2022 49
2023 45
2024 33
2025 15
Ameren Illinois Company  
Finite-Lived Intangible Assets [Line Items]  
2021 46
2022 42
2023 34
2024 21
2025 $ 7