Quarterly report pursuant to Section 13 or 15(d)

Short term and Long term Investments, Restricted Deposits (Narrative) (Details)

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Short term and Long term Investments, Restricted Deposits (Narrative) (Details)
$ in Millions
 1 Months Ended 9 Months Ended
Jan. 31, 2016
USD ($)
shares
Sep. 30, 2016
position
Schedule Of Investments And Restricted Deposits By Type [Line Items]    
Investments recorded at fair value that carry rating of AA, weighted average (in years)   3 years 3 months 18 days
Percentage of acquisition 19.00%  
New stock issued (in shares) | shares 1,144,462  
Common stock issued for acquisition | $ $ 68  
Positions from which gross unrealized losses were generated   569
Total unrealized investment positions   2,731
Rated Securities | External Credit Rating, Investment Grade    
Schedule Of Investments And Restricted Deposits By Type [Line Items]    
Percentage of investments in rated securities carry an investment grade rating by S&P and Moody's   95.00%