FAIR VALUE MEASUREMENTS (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 603		$ 594
Gross unrealized gains	353		317
Gross unrealized losses	(4)		(3)
Estimated fair value	952		908
Proceeds from sales	134	129
Gross realized gains	5	4
Gross realized losses	3
Total Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost	357		325
Gross unrealized gains	20		25
Gross unrealized losses	(2)		(1)
Estimated fair value	375		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	170		147
Gross unrealized gains	8		9
Gross unrealized losses	(1)
Estimated fair value	177		156
Municipal Bonds
Schedule of Available-for-sale Securities [Line Items]
Cost	58		57
Gross unrealized gains	6		6
Estimated fair value	64		63
Other Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost	129		121
Gross unrealized gains	6		10
Gross unrealized losses	(1)		(1)
Estimated fair value	134		130
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Cost	238		249
Gross unrealized gains	333		292
Gross unrealized losses	(2)		(2)
Estimated fair value	569		539
Cash And Cash Equivalents
Schedule of Available-for-sale Securities [Line Items]
Cost	8		20
Estimated fair value	$ 8		$ 20