Fair Value Measurements (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair value option of contractual principal outstanding	$ 550	$ 550
Nonrecurring fair value of leased assets	50	50
Current liabilities, fair value	88	131
PSEG [Member]
Current liabilities, fair value	$ 50	$ 50

Fair values as of the balance sheet date of all liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments, and which are expected to be extinguished or otherwise disposed of within a year or the normal operating cycle, if longer, net of the effects of master netting arrangements.

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+ Details