FAIR VALUE MEASUREMENTS (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012	Jun. 30, 2013		Jun. 30, 2012	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 609			$ 609			$ 594
Gross unrealized gains	342			342			317
Gross unrealized losses	(13)			(13)			(3)
Estimated fair value	938			938			908
Proceeds from sales	192		191	326		320
Gross realized gains	6		5	11		9
Gross realized losses	4		5	7		5
Total Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost	374			374			325
Gross unrealized gains	9			9			25
Gross unrealized losses	(9)			(9)			(1)
Estimated fair value	374			374			349
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	163	[1]		163	[1]		147
Gross unrealized gains	4	[1]		4	[1]		9
Gross unrealized losses	(3)	[1]		(3)	[1]
Estimated fair value	164	[1]		164	[1]		156
Municipal Bonds
Schedule of Available-for-sale Securities [Line Items]
Cost	72	[2]		72	[2]		57
Gross unrealized gains	3	[2]		3	[2]		6
Gross unrealized losses	(1)	[2]		(1)	[2]
Estimated fair value	74	[2]		74	[2]		63
Other Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost	139	[3]		139	[3]		121
Gross unrealized gains	2	[3]		2	[3]		10
Gross unrealized losses	(5)	[3]		(5)	[3]		(1)
Estimated fair value	136	[3]		136	[3]		130
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Cost	230			230			249
Gross unrealized gains	333			333			292
Gross unrealized losses	(4)			(4)			(2)
Estimated fair value	559			559			539
Cash And Cash Equivalents
Schedule of Available-for-sale Securities [Line Items]
Cost	5			5			20
Estimated fair value	$ 5			$ 5			$ 20

[1] Maturity dates are 2013-2056.

[2] Maturity dates are 2013-2062.

[3] Maturity dates are 2013-2111.