Investments In Marketable Securities (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis	$ 676,000,000
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis	33,000,000
Available-for-sale Securities, Realized Losses, Excluding Other than Temporary Impairments	0	0	0
Gross proceeds from sales of AFS securities	4,569,000,000	4,406,000,000	6,489,000,000
Other than Temporary Impairment Losses, Investments	$ 0	$ 0	$ 0