SONGS NDT 1 (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				12 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 685				$ 675
Gross Unrealized Gains	477				466
Gross Unrealized Loss	(12)				(10)
Estimated fair value	1,150				1,131
Proceeds from sales	94	[1]	195	[1]
Gross realized gains	2		4
Gross realized losses	(4)		(4)
Total Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost	448				430
Gross Unrealized Gains	25				21
Gross Unrealized Loss	(8)				(6)
Estimated fair value	465				445
Debt Securities Issued By The U.S. Treasury And Other U.S. Government Corporations And Agencies
Schedule of Available-for-sale Securities [Line Items]
Cost	103	[2]			103
Gross Unrealized Gains	8	[2]			6
Gross Unrealized Loss	0	[2]			0
Estimated fair value	111	[2]			109
Municipal Bonds
Schedule of Available-for-sale Securities [Line Items]
Cost	134	[3]			121
Gross Unrealized Gains	8	[3]			8
Gross Unrealized Loss	0	[3]			0
Estimated fair value	142	[3]			129
Other Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost	211	[4]			206
Gross Unrealized Gains	9	[4]			7
Gross Unrealized Loss	(8)	[4]			(6)
Estimated fair value	212	[4]			207
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Cost	218				215
Gross Unrealized Gains	452				444
Gross Unrealized Loss	(4)				(4)
Estimated fair value	666				655
Cash And Cash Equivalents
Schedule of Available-for-sale Securities [Line Items]
Cost	19				30
Gross Unrealized Gains	0				1
Gross Unrealized Loss	0				0
Estimated fair value	$ 19				$ 31

[1] Excludes securities that are held to maturity.

[2] Maturity dates are 2015-2060.

[3] Maturity dates are 2015-2114.

[4] Maturity dates are 2015-2111.