Financing Receivables (Outstanding Loans by Class of Customer) (Detail) - PSE And G [Member] - USD ($) $ in Millions |
Mar. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Concentration Risk [Line Items] | ||
| Outstanding Loans by Class of Customer | $ 178 | $ 168 |
| Commercial/Industrial [Member] | ||
| Concentration Risk [Line Items] | ||
| Outstanding Loans by Class of Customer | 168 | 158 |
| Residential [Member] | ||
| Concentration Risk [Line Items] | ||
| Outstanding Loans by Class of Customer | $ 10 | $ 10 |