Fair Value Measurements (Schedule Of Unrealized Gains (Losses) Related To Available-For-Sale Investments) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,497	[1]	$ 1,478
Total Unrealized Gains	897	[1]	756
Total Unrealized Losses	(3)	[1]	(5)
Total Fair Value	2,391	[1]	2,229
Amount primarily related to deferred taxes on appreciation of investment value	236		188
Money Market Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	25		24
Total Fair Value	25		24
U.S. Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	328		334
Total Unrealized Gains	624		518
Total Unrealized Losses	(1)		(3)
Total Fair Value	951		849
Non-U.S. Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	198		194
Total Unrealized Gains	158		131
Total Unrealized Losses	(1)		(2)
Total Fair Value	355		323
U.S. Government And Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	765		774
Total Unrealized Gains	106		102
Total Unrealized Losses	(1)		0
Total Fair Value	870		876
Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	32		56
Total Unrealized Gains	4		2
Total Unrealized Losses	0		0
Total Fair Value	36		58
Other Fixed-Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	149		96
Total Unrealized Gains	5		3
Total Unrealized Losses	0		0
Total Fair Value	$ 154		$ 99

[1] Excludes $236 million and $188 million at September 30, 2012 and December 31, 2011, respectively, primarily related to deferred taxes on appreciation of investment value.