Callaway Energy Center (Cost and Fair Values of Investments In Debt Securities in Nuclear Decommissioning Trust Fund According to Contractual Maturities) (Details) $ in Millions	Dec. 31, 2024 USD ($)
Nuclear Waste Matters [Abstract]
Cost, Less than 5 years	$ 186
Cost, 5 years to 10 years	117
Cost, Due after 10 years	134
Cost, Total	437
Fair Value, Less than 5 years	184
Fair Value, 5 years to 10 years	112
Fair Value, Due after 10 years	126
Fair Value, Total	$ 422