Investments In Marketable Securities (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis	$ 549,000,000
Available-for-sale Securities, Debt Securities, Noncurrent	35,000,000
Gain Loss On Marketable Securities
Realized losses on the sale of available-for-sale securities	0	0
Other-than-temporary impairment of marketable securities	0	0
Gross proceeds from sales of available-for-sale securities	1,086,000,000	1,060,000,000
Available-for-sale Securities, Gross Realized Gain (Loss)- (Less than)	1,000,000	1,000,000
Trading Securities, Realized Gain (Loss)- (Less than)	$ 1,000,000	$ 1,000,000