Available-For-Sale Securities (Fair Value Of Rabbi Trust) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Total Rabbi Trust Available-for-Sale Securities	$ 196	$ 185
Power [Member]
Total Rabbi Trust Available-for-Sale Securities	38	36
PSE And G [Member]
Total Rabbi Trust Available-for-Sale Securities	61	61
Other Entity [Member]
Total Rabbi Trust Available-for-Sale Securities	97	88
Rabbi Trusts [Member] \| Equity Securities [Member]
Cost	13	13
Gross Unrealized Gains	6	5
Available-for-sale Securities, Gross Unrealized Losses	0	0
Fair Value	19	18
Rabbi Trusts [Member] \| Government Obligations [Member]
Cost	113	114
Gross Unrealized Gains	2	3
Available-for-sale Securities, Gross Unrealized Losses	0	0
Fair Value	115	117
Rabbi Trusts [Member] \| Other Debt Securities [Member]
Cost	46	45
Gross Unrealized Gains	1	2
Available-for-sale Securities, Gross Unrealized Losses	0	0
Fair Value	47	47
Rabbi Trusts [Member] \| Total Debt Securities [Member]
Cost	159	159
Gross Unrealized Gains	3	5
Available-for-sale Securities, Gross Unrealized Losses	0
Fair Value	162	164
Rabbi Trusts [Member] \| Total Debt Securities [Member]
Cost	187	175
Gross Unrealized Gains	9	10
Available-for-sale Securities, Gross Unrealized Losses	0	0
Fair Value	196	185
Rabbi Trusts [Member] \| Other Securities [Member]
Cost	15	3
Gross Unrealized Gains	0	0
Available-for-sale Securities, Gross Unrealized Losses	0	0
Fair Value	$ 15	$ 3

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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+ Details

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References+ Details

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

+ References+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details