Fair Value Measurements (Schedule Of Unrealized Gains (Losses) Related To Available-For-Sale Investments) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,516		$ 1,478
Total Unrealized Gains	870		756
Total Unrealized Losses	(4)		(5)
Total Fair Value	2,382	[1]	2,229	[1]
Amount primarily related to deferred taxes on appreciation of investment value	248		188
U.S. Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	319		334
Total Unrealized Gains	616		518
Total Unrealized Losses	(1)		(3)
Total Fair Value	934	[1]	849	[1]
Non-U.S. Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	197		194
Total Unrealized Gains	162		131
Total Unrealized Losses	(1)		(2)
Total Fair Value	358	[1]	323	[1]
U.S. Government And Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	787		798
Total Unrealized Gains	86		102
Total Unrealized Losses	(1)
Total Fair Value	872	[1]	900	[1]
Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	66		56
Total Unrealized Gains	3		2
Total Unrealized Losses	(1)
Total Fair Value	68	[1]	58	[1]
Other Fixed-Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	147		96
Total Unrealized Gains	3		3
Total Unrealized Losses
Total Fair Value	$ 150	[1]	$ 99	[1]

[1] Excludes $248 million and $188 million at March 31, 2012 and December 31, 2011, respectively, primarily related to deferred taxes on appreciation of investment value.