Financing Receivables (Schedule Of Assets Under Lease Receivables) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Shawville Station [Member]
Financing Receivable, Recorded Investment [Line Items]
Lease Receivable, Counterparties' S&P Credit Ratings	BB+
Merrill Creek Reservoir [Member]
Financing Receivable, Recorded Investment [Line Items]
Lease Receivable, Gross Investment	$ 26
Lease Receivable, Counterparty	Metropolitan Edison Company (a subsidiary of First Energy)