Quarterly report pursuant to Section 13 or 15(d)

Short-Term And Long-Term Investments And Restricted Deposits (Short-Term And Long-Term Investments And Restricted Deposits By Investment Type) (Details)

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Short-Term And Long-Term Investments And Restricted Deposits (Short-Term And Long-Term Investments And Restricted Deposits By Investment Type) (Details) (USD $)
In Thousands, unless otherwise specified
Jun. 30, 2014
Dec. 31, 2013
Schedule Of Investments And Restricted Deposits By Type [Line Items]    
Amortized Cost $ 1,198,999 $ 945,129
Fair Value 1,202,755 940,972
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments 7,414 4,788
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments (3,658) (8,945)
U.S. Treasury Securities And Obligations Of U.S. Government Corporations And Agencies [Member]
   
Schedule Of Investments And Restricted Deposits By Type [Line Items]    
Amortized Cost 325,602 246,085
Fair Value 322,677 238,836
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments 424 245
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments (3,349) (7,494)
Corporate Securities [Member]
   
Schedule Of Investments And Restricted Deposits By Type [Line Items]    
Amortized Cost 395,427 293,912
Fair Value 399,348 296,086
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments 4,087 2,782
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments (166) (608)
Restricted Certificates Of Deposit [Member]
   
Schedule Of Investments And Restricted Deposits By Type [Line Items]    
Amortized Cost 5,892 5,891
Fair Value 5,892 5,891
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments 0 0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments 0 0
Restricted Cash Equivalents [Member]
   
Schedule Of Investments And Restricted Deposits By Type [Line Items]    
Amortized Cost 57,608 26,642
Fair Value 57,608 26,642
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments 0 0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments 0 0
Municipal Securities, General Obligation [Member]
   
Schedule Of Investments And Restricted Deposits By Type [Line Items]    
Amortized Cost 38,950 54,003
Fair Value 39,408 54,422
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments 480 555
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments (22) (136)
Municipal Securities, Pre-Refunded [Member]
   
Schedule Of Investments And Restricted Deposits By Type [Line Items]    
Amortized Cost 8,486 10,835
Fair Value 8,535 10,917
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments 59 82
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments (10) 0
Municipal Securities, Revenue [Member]
   
Schedule Of Investments And Restricted Deposits By Type [Line Items]    
Amortized Cost 68,871 68,801
Fair Value 69,400 69,054
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments 571 545
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments (42) (292)
Municipal Securities, Variable Rate Demand Notes [Member]
   
Schedule Of Investments And Restricted Deposits By Type [Line Items]    
Amortized Cost 18,000 28,575
Fair Value 18,000 28,575
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments 0 0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments 0 0
Asset Backed Securities [Member]
   
Schedule Of Investments And Restricted Deposits By Type [Line Items]    
Amortized Cost 179,418 138,803
Fair Value 179,985 139,050
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments 636 579
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments (69) (332)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
   
Schedule Of Investments And Restricted Deposits By Type [Line Items]    
Amortized Cost 47,113 33,974
Fair Value 48,270 33,891
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments 1,157 0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments 0 (83)
Cost And Equity Method Investments [Member]
   
Schedule Of Investments And Restricted Deposits By Type [Line Items]    
Amortized Cost 38,087 22,239
Fair Value 38,087 22,239
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments 0 0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments 0 0
Life Insurance Contracts [Member]
   
Schedule Of Investments And Restricted Deposits By Type [Line Items]    
Amortized Cost 15,545 15,369
Fair Value 15,545 15,369
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments 0 0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments $ 0 $ 0