XML 23 R37.htm IDEA: XBRL DOCUMENT v2.4.0.6
INVESTMENTS (Details 3) (USD $)
In Thousands, unless otherwise specified
9 Months Ended
Sep. 30, 2012
D
Dec. 31, 2011
INVESTMENTS    
Number of days for settlement basis, VRDNs to be liquidated at par 7  
Disclosure of underlying contractual maturities of investments    
Amortized Cost $ 327,536 $ 434,476
Fair Value 327,495 434,420
U.S. Treasuries | Less than 1 year
   
Disclosure of underlying contractual maturities of investments    
Amortized Cost   8,034
Fair Value   8,039
Certificates of deposit | Less than 1 year
   
Disclosure of underlying contractual maturities of investments    
Amortized Cost 17,015 29,034
Fair Value 17,017 29,035
Corporate bonds | Less than 1 year
   
Disclosure of underlying contractual maturities of investments    
Amortized Cost   2,022
Fair Value   2,022
Municipal securities | Less than 1 year
   
Disclosure of underlying contractual maturities of investments    
Amortized Cost 253,283 284,605
Fair Value 253,237 284,541
U.S. government agency securities | Less than 1 year
   
Disclosure of underlying contractual maturities of investments    
Amortized Cost 29,982 16,005
Fair Value 29,985 16,007
Variable rate demand notes | Due 1 - 10 years
   
Disclosure of underlying contractual maturities of investments    
Amortized Cost   5,775
Fair Value   5,775
Variable rate demand notes | Due 11 - 20 years
   
Disclosure of underlying contractual maturities of investments    
Amortized Cost 3,000 12,716
Fair Value 3,000 12,716
Variable rate demand notes | Due 21 - 30 years
   
Disclosure of underlying contractual maturities of investments    
Amortized Cost 2,501 27,902
Fair Value 2,501 27,902
Variable rate demand notes | Due 31 - 40 years
   
Disclosure of underlying contractual maturities of investments    
Amortized Cost 1,000 12,532
Fair Value 1,000 12,532
Auction rate securities | Due 11 - 20 years
   
Disclosure of underlying contractual maturities of investments    
Amortized Cost 10,896 5,158
Fair Value 10,896 5,158
Auction rate securities | Due 21 - 30 years
   
Disclosure of underlying contractual maturities of investments    
Amortized Cost 9,859 25,134
Fair Value 9,859 25,134
Auction rate securities | Due 31 - 40 years
   
Disclosure of underlying contractual maturities of investments    
Amortized Cost   5,559
Fair Value   $ 5,559