Commitments and Contingencies (Nuclear Insurance) (Detail) - USD ($) $ in Millions	3 Months Ended
	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
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	$ 415