Commitments and Contingencies (Nuclear Insurance) (Detail) - USD ($) $ in Millions	1 Months Ended		3 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Jun. 30, 2022	Mar. 31, 2022
Loss Contingencies [Line Items]
Maximum assessment for premiums on insurance policy			$ 65
Summer
Loss Contingencies [Line Items]
NRC minimum requirement		$ 1,060	1,060
Property insurance coverage				$ 2,750
Summer | DESC | European Mutual Association for Nuclear Insurance
Loss Contingencies [Line Items]
Property damage and outage costs coverage from non-nuclear origin event		1	$ 1	$ 415
Secondary Financial Protection Program | Nuclear Plant
Loss Contingencies [Line Items]
Maximum liability protection per nuclear incident amount	$ 13,700	$ 13,500