Investments In Marketable Securities (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis	$ 628,000,000		$ 628,000,000
Available-for-sale Securities, Debt Securities, Noncurrent	31,000,000		31,000,000
Gain Loss On Marketable Securities
Realized losses on the sale of available-for-sale securities	0	0	0	0
Other-than-temporary impairment of marketable securities	0	0	0	0
Gross proceeds from sales of available-for-sale securities	$ 1,144,000,000	$ 1,071,000,000	$ 3,362,000,000	$ 3,394,000,000