SONGS NDT 1 (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended			12 Months Ended
		Sep. 30, 2015		Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 681			$ 681			$ 675
Gross Unrealized Gains					397			466
Gross Unrealized Loss					(18)			(10)
Estimated fair value		1,060			1,060			1,131
Proceeds from sales	[1]	210		$ 148	431		$ 498
Gross realized gains		18		5	24		9
Gross realized losses		(6)		$ (3)	(13)		$ (8)
Total Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost		451			451			430
Gross Unrealized Gains					15			21
Gross Unrealized Loss					(12)			(6)
Estimated fair value		454			454			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		90	[2]		90	[2]		103
Gross Unrealized Gains					5	[2]		6
Gross Unrealized Loss					0	[2]		0
Estimated fair value		95	[2]		95	[2]		109
Municipal Bonds
Schedule of Available-for-sale Securities [Line Items]
Cost		147	[3]		147	[3]		121
Gross Unrealized Gains					7	[3]		8
Gross Unrealized Loss					0	[3]		0
Estimated fair value		154	[3]		154	[3]		129
Other Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost		214	[3]		214	[3]		206
Gross Unrealized Gains					3	[3]		7
Gross Unrealized Loss					(12)	[3]		(6)
Estimated fair value		205	[3]		205	[3]		207
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Cost		212			212			215
Gross Unrealized Gains					382			444
Gross Unrealized Loss					(6)			(4)
Estimated fair value		588			588			655
Cash And Cash Equivalents
Schedule of Available-for-sale Securities [Line Items]
Cost		18			18			30
Gross Unrealized Gains					0			1
Gross Unrealized Loss					0			0
Estimated fair value		$ 18			$ 18			$ 31

[1] Excludes securities that are held to maturity.

[2] Maturity dates are 2016-2065.

[3] Maturity dates are 2015-2115.