Fair Value Measurements (Schedule Of Unrealized Gains (Losses) Related To Available-For-Sale Investments) (Detail) (USD $)	Jun. 30, 2012		Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,498		$ 1,478
Total Unrealized Gains	825		756
Total Unrealized Losses	(7)		(5)
Total Fair Value	2,316	[1]	2,229	[1]
Amount primarily related to deferred taxes on appreciation of investment value	210,000,000		188,000,000
U.S. Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	325		334
Total Unrealized Gains	576		518
Total Unrealized Losses	(2)		(3)
Total Fair Value	899	[1]	849	[1]
Non-U.S. Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	197		194
Total Unrealized Gains	137		131
Total Unrealized Losses	(4)		(2)
Total Fair Value	330	[1]	323	[1]
U.S. Government And Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	748		798
Total Unrealized Gains	104		102
Total Unrealized Losses	(1)
Total Fair Value	851	[1]	900	[1]
Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	54		56
Total Unrealized Gains	3		2
Total Fair Value	57	[1]	58	[1]
Other Fixed-Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	174		96
Total Unrealized Gains	5		3
Total Fair Value	$ 179	[1]	$ 99	[1]

[1] Excludes $210 million and $188 million at June 30, 2012 and December 31, 2011, respectively, primarily related to deferred taxes on appreciation of investment value.