Pension, OPEB and Savings Plans (Fair Value Measurements And The Levels Of Inputs Used In Determining Fair Values) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 5,654		$ 5,435
Temporary Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	153	[1]	93	[1]
Common Stocks Commingled - US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,292	[2]	2,264	[2]
Common Stocks Commingled - International [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,005	[2]	1,016	[2]
Common Stocks Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	727	[2]	704	[2]
Government (US & Foreign) Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	509	[3]	596	[3]
Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	943	[3]	737	[3]
Private Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	25	[4]	25	[4]
Quoted Market Prices for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,116		4,036
Quoted Market Prices for Identical Assets (Level 1) [Member] | Temporary Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	92	[1]	52	[1]
Quoted Market Prices for Identical Assets (Level 1) [Member] | Common Stocks Commingled - US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,292	[2]	2,264	[2]
Quoted Market Prices for Identical Assets (Level 1) [Member] | Common Stocks Commingled - International [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,005	[2]	1,016	[2]
Quoted Market Prices for Identical Assets (Level 1) [Member] | Common Stocks Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	727	[2]	704	[2]
Quoted Market Prices for Identical Assets (Level 1) [Member] | Government (US & Foreign) Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[3]	0	[3]
Quoted Market Prices for Identical Assets (Level 1) [Member] | Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[3]	0	[3]
Quoted Market Prices for Identical Assets (Level 1) [Member] | Private Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[4]	0	[4]
Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,513		1,374
Significant Other Observable Inputs (Level 2) [Member] | Temporary Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	61	[1]	41	[1]
Significant Other Observable Inputs (Level 2) [Member] | Common Stocks Commingled - US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[2]	0	[2]
Significant Other Observable Inputs (Level 2) [Member] | Common Stocks Commingled - International [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[2]	0	[2]
Significant Other Observable Inputs (Level 2) [Member] | Common Stocks Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[2]	0	[2]
Significant Other Observable Inputs (Level 2) [Member] | Government (US & Foreign) Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	509	[3]	596	[3]
Significant Other Observable Inputs (Level 2) [Member] | Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	943	[3]	737	[3]
Significant Other Observable Inputs (Level 2) [Member] | Private Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[4]	0	[4]
Pension And OPEB Plans Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	25		25
Pension And OPEB Plans Level 3 [Member] | Temporary Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[1]	0	[1]
Pension And OPEB Plans Level 3 [Member] | Common Stocks Commingled - US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[2]	0	[2]
Pension And OPEB Plans Level 3 [Member] | Common Stocks Commingled - International [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[2]	0	[2]
Pension And OPEB Plans Level 3 [Member] | Common Stocks Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[2]	0	[2]
Pension And OPEB Plans Level 3 [Member] | Government (US & Foreign) Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[3]	0	[3]
Pension And OPEB Plans Level 3 [Member] | Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[3]	0	[3]
Pension And OPEB Plans Level 3 [Member] | Private Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	25	[4]	25	[4]	31
Long Island Electric Utility Servco LLC Pension and OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	69
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Temporary Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	[5]
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Common Stocks Commingled - US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48	[6]
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	20	[3]
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Quoted Market Prices for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Quoted Market Prices for Identical Assets (Level 1) [Member] | Temporary Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[5]
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Quoted Market Prices for Identical Assets (Level 1) [Member] | Common Stocks Commingled - US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48	[6]
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Quoted Market Prices for Identical Assets (Level 1) [Member] | Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[3]
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Significant Other Observable Inputs (Level 2) [Member] | Temporary Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	[5]
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Significant Other Observable Inputs (Level 2) [Member] | Common Stocks Commingled - US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[6]
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	20	[3]
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Pension And OPEB Plans Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Pension And OPEB Plans Level 3 [Member] | Temporary Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[5]
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Pension And OPEB Plans Level 3 [Member] | Common Stocks Commingled - US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	[6]
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Pension And OPEB Plans Level 3 [Member] | Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	[3]

[1] Certain open-ended mutual funds with mainly short-term investments are valued based on unadjusted quoted prices in active market (Level 1). Certain temporary investments are valued using inputs such as time-to-maturity, coupon rate, quality rating and current yield (Level 2).

[2] Wherever possible, fair values of equity investments in stocks and in commingled funds are derived from quoted market prices as substantially all of these instruments have active markets (primarily Level 1). Most investments in stocks are priced utilizing the principal market close price or in some cases midpoint, bid or ask price.

[3] Investments in fixed income securities including bond funds are priced using an evaluated pricing approach or the most recent exchange or quoted bid (primarily Level 2).

[4] Limited partnership interests in private equity funds are valued using significant unobservable inputs as there is little, if any, market activity. In addition, there may be transfer restrictions on private equity securities. The process for determining the fair value of such securities relied on commonly accepted valuation techniques, including the use of earnings multiples based on comparable public securities, industry-specific non-earnings-based multiples and discounted cash flow models. These inputs require significant management judgment or estimation (primarily Level 3).

[5] Certain temporary investments are valued using inputs such as time-to-maturity, coupon rate, quality rating and current yield (Level 2).

[6] Wherever possible, fair values of equity investments in commingled stock funds are derived from quoted market prices as substantially all of these instruments have active markets (primarily Level 1). Most investments in stocks are priced utilizing the principal market close price or in some cases midpoint, bid or ask price.