Fair Value (Fair Value of Fixed Income Securities Held in Nuclear Decommissioning Trust Funds (Details) - Fixed income securities - Nuclear decommissioning trust fund $ in Millions	Sep. 30, 2023 USD ($)
Debt Securities, Available-for-sale [Line Items]
Due within one year	$ 7
Due after one through five years	105
Due after five through ten years	86
Due after ten years	253
Fixed income securities total	$ 451