Fair Value (Fair Value of Fixed Income Securities Held in Nuclear Decommissioning Trust Funds (Details) - Fixed income securities - Nuclear decommissioning trust fund $ in Millions	Mar. 31, 2025 USD ($)
Debt Securities, Available-for-sale [Line Items]
Due within one year	$ 15
Due after one through five years	107
Due after five through ten years	101
Due after ten years	322
Fixed income securities total	$ 545