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 Thousands, unless otherwise specified
Sep. 30, 2013
Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Months, Unrealized Losses $ (7,744) $ (490)
Less Than 12 Months, Fair Value 350,400 121,901
12 Months or More, Unrealized Losses (66) (2)
12 Months or More, Fair Value 4,302 202
U.S. Treasury Securities And Obligations Of U.S. Government Corporations And Agencies [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Months, Unrealized Losses (6,196) (219)
Less Than 12 Months, Fair Value 196,888 56,033
12 Months or More, Unrealized Losses 0 (2)
12 Months or More, Fair Value 0 202
Corporate Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Months, Unrealized Losses (641) (198)
Less Than 12 Months, Fair Value 79,753 44,758
12 Months or More, Unrealized Losses (9) 0
12 Months or More, Fair Value 42 0
Municipal Securities, General Obligation [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Months, Unrealized Losses (119) (26)
Less Than 12 Months, Fair Value 9,264 8,464
12 Months or More, Unrealized Losses (50) 0
12 Months or More, Fair Value 2,453 0
Municipal Securities, Pre-Refunded [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Months, Unrealized Losses (1) 0
Less Than 12 Months, Fair Value 489 0
12 Months or More, Unrealized Losses 0 0
12 Months or More, Fair Value 0 0
Municipal Securities, Revenue [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Months, Unrealized Losses (531) (30)
Less Than 12 Months, Fair Value 28,866 3,325
12 Months or More, Unrealized Losses (7) 0
12 Months or More, Fair Value 1,807 0
Asset Backed Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Months, Unrealized Losses (256) (17)
Less Than 12 Months, Fair Value 35,140 9,321
12 Months or More, Unrealized Losses 0 0
12 Months or More, Fair Value $ 0 $ 0