Marketable Securities (Investments In Debt And Equity Securities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Cost of marketable securities	$ 942	$ 1,295
Unrealized gains on marketable securities	1	3
Unrealized losses on marketable securities	(2)	(5)
Fair value of marketable securities	941	1,293
United States Government Obligations [Member] | Maturity Less Than 1 Year [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	395	548
Fair Value	395	548
United States Government Obligations [Member] | Maturity 1 To 5 Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	124	93
Fair Value	124	93
Government-Sponsored Enterprise Obligations [Member] | Maturity 1 To 5 Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	4	2
Fair Value	4	2
Corporate Debt Securities [Member] | Maturity 1 To 5 Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	16	15
Fair Value	16	15
Other Debt Instruments [Member] | Maturity Less Than 1 Year [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	38	28
Fair Value	38	28
Other Debt Instruments [Member] | Maturity 1 To 5 Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	3	3
Fair Value	3	3
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	362	606
Available-for-sale Securities, Gross Unrealized Gain, Accumulated in Investments	1	3
Available-for-sale Securities, Gross Unrealized Loss, Accumulated in Investments	(2)	(5)
Fair Value	$ 361	$ 604