v2.4.0.8
Fair Value Measurements (Fair Value Measurements By Level For Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2014
Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash and Cash Equivalents $ 1,523,596 $ 974,304
U.S. Treasury securities and obligations of U.S. government corporations and agencies 310,572 224,423
Corporate securities 491,129 296,086
Municipal securities, General obligation 49,875 54,422
Municipal securities, Pre-refunded 4,985 10,917
Municipal securities, Revenue 101,022 69,054
Municipal securities, Variable rate demand notes 11,700 28,575
Asset backed securities 185,516 139,050
Mortgage backed securities 46,776 33,891
Total investments 1,201,575 856,418
Cash and cash equivalents 78,995 26,642
Certificates of deposit 5,892 5,891
U.S. Treasury securities and obligations of U.S. government corporations and agencies 14,840 14,413
Total restricted deposits 99,727 46,946
Other long-term assets: Interest rate swap agreements 6,796 9,576
Total assets at fair value 2,831,694 1,887,244
Interest Rate Derivative Liabilities, at Fair Value 1,250  
Liabilities, Fair Value Disclosure, Recurring 1,250  
Level I [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash and Cash Equivalents 1,523,596 974,304
U.S. Treasury securities and obligations of U.S. government corporations and agencies 270,857 212,185
Corporate securities 0 0
Municipal securities, General obligation 0 0
Municipal securities, Pre-refunded 0 0
Municipal securities, Revenue 0 0
Municipal securities, Variable rate demand notes 0 0
Asset backed securities 0 0
Mortgage backed securities 0 0
Total investments 270,857 212,185
Cash and cash equivalents 78,995 26,642
Certificates of deposit 5,892 5,891
U.S. Treasury securities and obligations of U.S. government corporations and agencies 14,840 14,413
Total restricted deposits 99,727 46,946
Other long-term assets: Interest rate swap agreements 0 0
Total assets at fair value 1,894,180 1,233,435
Interest Rate Derivative Liabilities, at Fair Value 0  
Liabilities, Fair Value Disclosure, Recurring 0  
Level II [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash and Cash Equivalents 0 0
U.S. Treasury securities and obligations of U.S. government corporations and agencies 39,715 12,238
Corporate securities 491,129 296,086
Municipal securities, General obligation 49,875 54,422
Municipal securities, Pre-refunded 4,985 10,917
Municipal securities, Revenue 101,022 69,054
Municipal securities, Variable rate demand notes 11,700 28,575
Asset backed securities 185,516 139,050
Mortgage backed securities 46,776 33,891
Total investments 930,718 644,233
Cash and cash equivalents 0 0
Certificates of deposit 0 0
U.S. Treasury securities and obligations of U.S. government corporations and agencies 0 0
Total restricted deposits 0 0
Other long-term assets: Interest rate swap agreements 6,796 9,576
Total assets at fair value 937,514 653,809
Level III [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash and Cash Equivalents 0 0
U.S. Treasury securities and obligations of U.S. government corporations and agencies 0 0
Corporate securities 0 0
Municipal securities, General obligation 0 0
Municipal securities, Pre-refunded 0 0
Municipal securities, Revenue 0 0
Municipal securities, Variable rate demand notes 0 0
Asset backed securities 0 0
Mortgage backed securities 0 0
Total investments 0 0
Cash and cash equivalents 0 0
Certificates of deposit 0 0
U.S. Treasury securities and obligations of U.S. government corporations and agencies 0 0
Total restricted deposits 0 0
Other long-term assets: Interest rate swap agreements 0 0
Total assets at fair value 0 0
Interest Rate Derivative Liabilities, at Fair Value 0  
Liabilities, Fair Value Disclosure, Recurring $ 0