Income Taxes (Narrative) (Detail)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2017
Income Taxes [Line Items]
Effective Income Tax Rate, Federal and State Statutory Income Tax Rate, Percent	28.11%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	35.00%
NJ surcharge tax percent for 2018 to 2019	2.50%
NJ tax surcharge percent for 2020 to 2021	1.50%
PSE And G [Member]
Income Taxes [Line Items]
Effective Income Tax Rate, Federal and State Statutory Income Tax Rate, Percent	28.11%
Power [Member]
Income Taxes [Line Items]
Effective Income Tax Rate, Federal and State Statutory Income Tax Rate, Percent	28.11%