Fair Value Measurements (Schedule Of Unrealized Gains Losses Related To Available-For-Sale Investments) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amount primarily related to deferred taxes on appreciation of investment value	$ 324		$ 313
Cash And Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	17		38
Total Fair Value	17		38
U.S. Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost			246
Total Unrealized Gains			811
Total Unrealized Losses			0
Total Fair Value			1,057
Non-U.S. Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost			215
Total Unrealized Gains			242
Total Unrealized Losses			0
Total Fair Value			457
Global equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	520
Total Unrealized Gains	1,087
Total Unrealized Losses	(9)
Total Fair Value	1,598
U.S. Government And Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost			870
Total Unrealized Gains			51
Total Unrealized Losses			(5)
Total Fair Value			916
Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost			24
Total Unrealized Gains			2
Total Unrealized Losses			(1)
Total Fair Value			25
Fixed-Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,059		163
Total Unrealized Gains	75		1
Total Unrealized Losses	(4)		(2)
Total Fair Value	1,130		162
Securities (Assets) [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,601		1,569
Total Unrealized Gains	1,190		1,178
Total Unrealized Losses	(13)		(8)
Total Fair Value	2,778		2,739
Other securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5		13
Total Unrealized Gains	28		71
Total Unrealized Losses	0		0
Total Fair Value	33		84
Nuclear Decommissioning Trusts [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,596	[1]	1,556	[1]
Total Unrealized Gains	1,162	[1]	1,107	[1]
Total Unrealized Losses	(13)	[1]	(8)	[1]
Total Fair Value	$ 2,745	[1]	$ 2,655	[1]

[1] Represents amounts before deducting $324 million and $313 million at December 31, 2014 and 2013, respectively, primarily related to deferred taxes on appreciation of investment value.