SONGS NDT 1 (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended			12 Months Ended
		Jun. 30, 2016		Jun. 30, 2015	Jun. 30, 2016		Jun. 30, 2015	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 671			$ 671			$ 660
Gross Unrealized Gains					443			423
Gross Unrealized Loss					(11)			(20)
Estimated fair value		1,103			1,103			1,063
Proceeds from sales	[1]	111		$ 127	204		$ 221
Gross realized gains		5		4	8		6
Gross realized losses		(3)		$ (3)	(11)		$ (7)
Total Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost		438			438			431
Gross Unrealized Gains					27			11
Gross Unrealized Loss					(6)			(13)
Estimated fair value		459			459			429
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		99	[2]		99	[2]		89
Gross Unrealized Gains					5	[2]		2
Gross Unrealized Loss					0	[2]		0
Estimated fair value		104	[2]		104	[2]		91
Municipal Bonds
Schedule of Available-for-sale Securities [Line Items]
Cost		150	[3]		150	[3]		148
Gross Unrealized Gains					13	[3]		8
Gross Unrealized Loss					0	[3]		0
Estimated fair value		163	[3]		163	[3]		156
Other Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost		189	[3]		189	[3]		194
Gross Unrealized Gains					9	[3]		1
Gross Unrealized Loss					(6)	[3]		(13)
Estimated fair value		192	[3]		192	[3]		182
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Cost		221			221			214
Gross Unrealized Gains					416			412
Gross Unrealized Loss					(5)			(7)
Estimated fair value		632			632			619
Cash And Cash Equivalents
Schedule of Available-for-sale Securities [Line Items]
Cost		12			12			15
Gross Unrealized Gains					0			0
Gross Unrealized Loss					0			0
Estimated fair value		$ 12			$ 12			$ 15

[1] Excludes securities that are held to maturity.

[2] Maturity dates are 2017-2065.

[3] Maturity dates are 2016-2115.