Quarterly report pursuant to Section 13 or 15(d)

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

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Investments And Restricted Deposits (Short-Term And Long-Term Investments And Restricted Deposits By Investment Type) (Details) (USD $)
In Thousands
Sep. 30, 2011
Dec. 31, 2010
Amortized Cost $ 652,840 $ 629,758
Gross Unrealized Gains 11,556 11,015
Gross Unrealized Losses (832) (790)
Fair Value 663,564 639,983
U.S. Treasury Securities And Obligations Of U.S. Government Corporations And Agencies [Member]
   
Amortized Cost 29,045 28,665
Gross Unrealized Gains 691 510
Gross Unrealized Losses (2) (140)
Fair Value 29,734 29,035
Corporate Securities [Member]
   
Amortized Cost 189,380 197,577
Gross Unrealized Gains 3,825 3,124
Gross Unrealized Losses (757) (586)
Fair Value 192,448 200,115
Restricted Certificates Of Deposit [Member]
   
Amortized Cost 5,890 6,814
Gross Unrealized Gains    
Gross Unrealized Losses    
Fair Value 5,890 6,814
Restricted Cash Equivalents [Member]
   
Amortized Cost 13,488 8,814
Gross Unrealized Gains    
Gross Unrealized Losses    
Fair Value 13,488 8,814
Municipal Securities, General Obligation [Member]
   
Amortized Cost 117,544 109,866
Gross Unrealized Gains 3,167 3,601
Gross Unrealized Losses (57) (6)
Fair Value 120,654 113,461
Municipal Securities, Pre-Refunded [Member]
   
Amortized Cost 32,682 32,442
Gross Unrealized Gains 613 756
Gross Unrealized Losses    
Fair Value 33,295 33,198
Municipal Securities, Revenue [Member]
   
Amortized Cost 114,675 100,198
Gross Unrealized Gains 2,768 2,781
Gross Unrealized Losses (16) (15)
Fair Value 117,427 102,964
Municipal Securities, Variable Rate Demand Notes [Member]
   
Amortized Cost 108,723 106,540
Gross Unrealized Gains    
Gross Unrealized Losses    
Fair Value 108,723 106,540
Asset Backed Securities [Member]
   
Amortized Cost 18,714 17,391
Gross Unrealized Gains 492 243
Gross Unrealized Losses   (43)
Fair Value 19,206 17,591
Cost Method Investments And Equity Method Securities [Member]
   
Amortized Cost 8,076 7,060
Gross Unrealized Gains    
Gross Unrealized Losses    
Fair Value 8,076 7,060
Life Insurance Contracts [Member]
   
Amortized Cost 14,623 14,391
Gross Unrealized Gains    
Gross Unrealized Losses    
Fair Value $ 14,623 $ 14,391