Derivative Instruments and Hedging Activities - Offsetting Derivative Instruments and Credit Risk-Related Features (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Assets [Abstract]
Cash collateral received - eligible for offset	$ 0	$ 0
Liabilities [Abstract]
Cash collateral pledged - eligible for offset	0	0
Credit Risk-Related Contingent Features [Abstract]
Aggregate fair value of additional collateral requirements in the event of a credit downgrade below investment grade	3
Derivative, Net Liability Position, Aggregate Fair Value	3
Treasury Derivatives [Member]
Assets [Abstract]
Gross	4	9
Derivative instruments - eligible for offset	3	5
Cash collateral received - eligible for offset	0	0
Net	1	4
Liabilities [Abstract]
Gross	16	16
Derivative instruments - eligible for offset	3	5
Cash collateral pledged - eligible for offset	0	0
Net	13	11
Louisville Gas And Electric Co [Member]
Assets [Abstract]
Cash collateral received - eligible for offset	0	0
Liabilities [Abstract]
Cash collateral pledged - eligible for offset	0	0
Louisville Gas And Electric Co [Member] | Treasury Derivatives [Member]
Assets [Abstract]
Gross	0	0
Derivative instruments - eligible for offset	0	0
Cash collateral received - eligible for offset	0	0
Net	0	0
Liabilities [Abstract]
Gross	5	3
Derivative instruments - eligible for offset	0	0
Cash collateral pledged - eligible for offset	0	0
Net	$ 5	$ 3