Fair Value Measurements (Narrative) (Details) (USD $)	3 Months Ended			12 Months Ended			3 Months Ended			12 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2011	Mar. 31, 2011	Jun. 30, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 PSEG [Member]	Dec. 31, 2010 Power [Member]	Jun. 30, 2010 Power [Member]	Dec. 31, 2011 Power [Member]	Dec. 31, 2010 Significant Other Observable Inputs (Level 2) [Member]	Dec. 31, 2010 Pension And OPEB Plans Level 3 [Member]	Dec. 31, 2010 Pension And OPEB Plans Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net assets measured at fair value on a recurring basis	$ 1,600,000,000			$ 1,600,000,000	$ 1,700,000,000
Net assets measured at fair value on a recurring basis measured using unobservable inputs	29,000,000			29,000,000	55,000,000
Level 3 net assets as a percentage of total assets	1.00%			1.00%	1.00%
Assets transferred from Level 3 to Level 2	33,000,000	33,000,000		8,000,000
Fair value option of contractual principal outstanding	550,000,000			550,000,000
Current liabilities, fair value	131,000,000			131,000,000	103,000,000	50,000,000	91,000,000		124,000,000
Nonrecurring fair values of leased assets	50,000,000			50,000,000
Pre-tax impairment charges			10,000,000				3,000,000
Emission valuation allowances								15,000,000		3,000,000		1,000,000
After-tax impairment charge											$ 6,000,000