Investments In Marketable Securities (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis	$ 411,000,000		$ 411,000,000
Available-for-sale Securities, Debt Securities, Noncurrent	33,000,000		33,000,000
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 AFS securities	1,395,000,000	1,158,000,000	2,481,000,000	2,218,000,000
Available-for-sale Securities, Gross Realized Gain (Loss)- (Less than)	1,000,000	1,000,000	1,000,000	1,000,000
Trading Securities, Realized Gain (Loss)- (Less than)	$ 1,000,000	$ 1,000,000	$ 1,000,000	$ 1,000,000