Fair Value Measurements (Schedule Of Unrealized Gains Losses Related To Available-For-Sale Investments) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amount primarily related to deferred taxes on appreciation of investment value		$ 314		$ 324
Money Market Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		36		17
Total Unrealized Gains		0		0
Total Unrealized Losses		0		0
Total Fair Value		36		17
Global equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		508		520
Total Unrealized Gains		1,034		1,087
Total Unrealized Losses		(9)		(9)
Total Fair Value		1,533		1,598
Fixed-Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		1,165		1,059
Total Unrealized Gains		58		75
Total Unrealized Losses		(8)		(4)
Total Fair Value		1,215		1,130
Securities (Assets) [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		1,709	[1],[2]	1,601
Total Unrealized Gains		1,092	[1],[2]	1,190
Total Unrealized Losses		(17)	[1],[2]	(13)
Total Fair Value		$ 2,784	[1],[2]	2,778
Other securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost				5
Total Unrealized Gains				28
Total Unrealized Losses				0
Total Fair Value				33
Nuclear Decommissioning Trusts [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	[1]			1,596
Total Unrealized Gains	[1]			1,162
Total Unrealized Losses	[1]			(13)
Total Fair Value	[1]			$ 2,745

[1] Represents amount before deducting $324 million, primarily related to deferred taxes on appreciation of investment value.

[2] Represents amounts before deducting $314 million and $324 million at December 31, 2015 and 2014, respectively, primarily related to deferred taxes on appreciation of investment value.