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Commitments And Contingent Liabilities (Regulatory Proceedings) (Detail) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Mar. 31, 2014
Sep. 30, 2017
Dec. 31, 2016
Loss Contingencies [Line Items]      
Clean Energy Program, current portion   $ 184 $ 142
PSE And G [Member]      
Loss Contingencies [Line Items]      
Clean Energy Program, current portion   184 $ 142
Power [Member] | FERC Compliance [Domain]      
Loss Contingencies [Line Items]      
Loss Contingency related to bidding errors $ 25 10  
Maximum [Member] | Power [Member] | FERC Compliance [Domain]      
Loss Contingencies [Line Items]      
Loss Contingency, Estimate of Possible Loss   135  
Minimum [Member] | Power [Member] | FERC Compliance [Domain]      
Loss Contingencies [Line Items]      
Loss Contingency, Estimate of Possible Loss   $ 35