Quarterly report pursuant to Section 13 or 15(d)

Short-Term And Long-Term Investments And Restricted Deposits (Fair Value Of Available-For-Sale Investments With Gross Unrealized Losses By Investment Type And Length Of Time) (Details)

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Short-Term And Long-Term Investments And Restricted Deposits (Fair Value Of Available-For-Sale Investments With Gross Unrealized Losses By Investment Type And Length Of Time) (Details) - USD ($)
$ in Millions
Jun. 30, 2015
Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]    
Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses Accumulated In Investments $ (4) $ (2)
Less Than 12 Months, Fair Value 625 491
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments 0 (2)
12 Months or More, Fair Value 70 198
U.S. Treasury Securities And Obligations Of U.S. Government Corporations And Agencies [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses Accumulated In Investments (1) 0
Less Than 12 Months, Fair Value 162 72
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments 0 (2)
12 Months or More, Fair Value 16 180
Corporate Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses Accumulated In Investments (2) (2)
Less Than 12 Months, Fair Value 286 311
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments 0 0
12 Months or More, Fair Value 31 1
Municipal Securities, General Obligation [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses Accumulated In Investments 0 0
Less Than 12 Months, Fair Value 51 4
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments 0 0
12 Months or More, Fair Value 3 3
Municipal Securities, Revenue [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses Accumulated In Investments (1) 0
Less Than 12 Months, Fair Value 52 16
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments 0 0
12 Months or More, Fair Value 5 3
Municipal Securities Pre Refunded [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses Accumulated In Investments 0 0
Less Than 12 Months, Fair Value 0 0
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments 0 0
12 Months or More, Fair Value 0 1
Asset Backed Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses Accumulated In Investments 0 0
Less Than 12 Months, Fair Value 37 70
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments 0 0
12 Months or More, Fair Value 15 10
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses Accumulated In Investments 0 0
Less Than 12 Months, Fair Value 37 18
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments 0 0
12 Months or More, Fair Value $ 0 $ 0