Investments Of Insurance Subsidiaries (Schedule Of Maturities Of Investments) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Due in one year or less	$ 72
Due after one year through five years	140
Due after five years through ten years	111
Due after ten years	93
Amortized Cost, Total	416
Amortized Cost	507
Due in one year or less	72
Fair Value	534	628
Due after one year through five years	149
Due after five years through ten years	119
Due after ten years	100
Fair Value, Total	440
Fair Value	526
Auction Rate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	76
Fair Value	71
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15
Fair Value	$ 15