Pension, OPEB and Savings Plans (Fair Value Measurements And The Levels Of Inputs Used In Determining Fair Values) (Details) - USD ($) $ in Millions		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 5,413		$ 5,654
Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	103		153
Common Stocks Commingled - US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	1,980		2,292
Common Stocks Commingled - International [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	987		1,005
Other Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	816		727
Government (US & Foreign) Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	602		509
Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	906		943
Private Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	19		25
Quoted Market Prices for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		3,885		4,116
Quoted Market Prices for Identical Assets (Level 1) [Member] | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	102		92
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]	1,980		2,292
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	[2]	987		1,005
Quoted Market Prices for Identical Assets (Level 1) [Member] | Other Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	816		727
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	[3]	0		0
Quoted Market Prices for Identical Assets (Level 1) [Member] | Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0		0
Quoted Market Prices for Identical Assets (Level 1) [Member] | Private Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0		0
Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1,509		1,513
Significant Other Observable Inputs (Level 2) [Member] | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	1		61
Significant Other Observable Inputs (Level 2) [Member] | Common Stocks Commingled - US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	0		0
Significant Other Observable Inputs (Level 2) [Member] | Common Stocks Commingled - International [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	0		0
Significant Other Observable Inputs (Level 2) [Member] | Other Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	0		0
Significant Other Observable Inputs (Level 2) [Member] | Government (US & Foreign) Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	602		509
Significant Other Observable Inputs (Level 2) [Member] | Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	906		943
Significant Other Observable Inputs (Level 2) [Member] | Private Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0		0
Pension And OPEB Plans Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		19		25
Pension And OPEB Plans Level 3 [Member] | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0		0
Pension And OPEB Plans Level 3 [Member] | Common Stocks Commingled - US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	0		0
Pension And OPEB Plans Level 3 [Member] | Common Stocks Commingled - International [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	0		0
Pension And OPEB Plans Level 3 [Member] | Other Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	0		0
Pension And OPEB Plans Level 3 [Member] | Government (US & Foreign) Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0		0
Pension And OPEB Plans Level 3 [Member] | Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0		0
Pension And OPEB Plans Level 3 [Member] | Private Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		19	[3]	25	[3]	$ 25
Long Island Electric Utility Servco LLC Pension and OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		97		69
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[4]	0		1
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	[5]	68		48
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[6]	29		20
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		68		48
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Quoted Market Prices for Identical Assets (Level 1) [Member] | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0	[4]
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		68		48	[5]
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		0	[6]
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		29		21
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Significant Other Observable Inputs (Level 2) [Member] | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		1	[4]
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		0	[5]
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		29		20	[6]
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		0
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Pension And OPEB Plans Level 3 [Member] | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0	[4]
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		0	[5]
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		$ 0	[6]

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

[5] 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.

[6] 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).