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, 2022 USD ($)
Nuclear Waste Matters [Abstract]
Cost, Less than 5 years	$ 154
Cost, 5 years to 10 years	92
Cost, Due after 10 years	128
Cost, Total	374
Fair Value, Less than 5 years	146
Fair Value, 5 years to 10 years	80
Fair Value, Due after 10 years	103
Fair Value, Total	$ 329