Marketable Securities (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Unrealized Gain, Accumulated in Investments	$ 2	$ 1
Available-for-sale Securities, Gross Unrealized Loss, Accumulated in Investments	(7)	(2)
Available-for-sale Securities, Amortized Cost Basis	871	942
Available-for-sale Securities	866	941
United States Government Obligations [Member] | Maturity Less Than 1 Year [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	282	395
Available-for-sale Securities, Gross Unrealized Gain, Accumulated in Investments	0	0
Available-for-sale Securities, Gross Unrealized Loss, Accumulated in Investments	0	0
Available-for-sale Securities, Debt Securities	282	395
United States Government Obligations [Member] | Maturity 1 To 5 Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	90	124
Available-for-sale Securities, Gross Unrealized Gain, Accumulated in Investments	0	0
Available-for-sale Securities, Gross Unrealized Loss, Accumulated in Investments	0	0
Available-for-sale Securities, Debt Securities	90	124
Government-Sponsored Enterprise Obligations [Member] | Maturity 1 To 5 Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1	4
Available-for-sale Securities, Gross Unrealized Gain, Accumulated in Investments	0	0
Available-for-sale Securities, Gross Unrealized Loss, Accumulated in Investments	0	0
Available-for-sale Securities, Debt Securities	1	4
Corporate Debt Securities [Member] | Maturity 1 To 5 Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	74	16
Available-for-sale Securities, Gross Unrealized Gain, Accumulated in Investments	0	0
Available-for-sale Securities, Gross Unrealized Loss, Accumulated in Investments	0	0
Available-for-sale Securities, Debt Securities	74	16
Other Debt Securities [Member] | Maturity Less Than 1 Year [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	66	38
Available-for-sale Securities, Gross Unrealized Gain, Accumulated in Investments	0	0
Available-for-sale Securities, Gross Unrealized Loss, Accumulated in Investments	0	0
Available-for-sale Securities, Debt Securities	66	38
Other Debt Securities [Member] | Maturity 1 To 5 Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	3	3
Available-for-sale Securities, Gross Unrealized Gain, Accumulated in Investments	0	0
Available-for-sale Securities, Gross Unrealized Loss, Accumulated in Investments	0	0
Available-for-sale Securities, Debt Securities	3	3
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Unrealized Gain, Accumulated in Investments	2	1
Available-for-sale Securities, Gross Unrealized Loss, Accumulated in Investments	(7)	(2)
Available-for-sale Equity Securities, Amortized Cost Basis	355	362
Available-for-sale Securities, Equity Securities	$ 350	$ 361