Marketable Securities (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Unrealized Gain, Accumulated in Investments	$ 33	$ 1
Available-for-sale Securities, Gross Unrealized Loss, Accumulated in Investments	(4)	(12)
Available-for-sale Securities, Amortized Cost Basis	884	1,011
Available-for-sale Securities	913us-gaap_AvailableForSaleSecurities	1,000us-gaap_AvailableForSaleSecurities
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	311	385
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	311	385
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	95	93
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	95	93
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	73	72
Available-for-sale Securities, Gross Unrealized Gain, Accumulated in Investments	1	0
Available-for-sale Securities, Gross Unrealized Loss, Accumulated in Investments	0	0
Available-for-sale Securities, Debt Securities	74	72
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	95	130
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	95	130
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	32	1
Available-for-sale Securities, Gross Unrealized Loss, Accumulated in Investments	(4)	(12)
Available-for-sale Equity Securities, Amortized Cost Basis	307	328
Available-for-sale Securities, Equity Securities	$ 335	$ 317

This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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