v2.4.0.6
Available-For-Sale Securities (Summary Of Available-For-Sale Debt And Equity Securities At Estimated Fair Value) (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2011
Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost, Total $ 9,109,173 $ 4,925,704
Gross Unrealized Gains 7,052 33,154
Gross Unrealized Losses (35,076) (9,720)
Estimated Fair Value, Debt securities 9,072,646 4,944,507
Estimated Fair Value, Equity securities 8,503 4,631
Estimated Fair Value, Total 9,081,149 4,949,138
Equity Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost, Equity securities 1,451 1,451
Gross Unrealized Gains 7,052 3,180
Gross Unrealized Losses 0 0
Estimated Fair Value, Equity securities 8,503 4,631
Debt Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost, Debt securities 9,107,722 4,924,253
Gross Unrealized Gains 0 29,974
Gross Unrealized Losses (35,076) (9,720)
Estimated Fair Value, Debt securities 9,072,646 4,944,507
Debt Securities [Member] | U.S. Treasury Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost, Debt securities 0 1,349,348
Gross Unrealized Gains 0 7,109
Gross Unrealized Losses 0 (1,020)
Estimated Fair Value, Debt securities 0 1,355,437
Debt Securities [Member] | Money Market Funds [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost, Debt securities 7,455,982 520,063
Gross Unrealized Gains 0 0
Gross Unrealized Losses 0 0
Estimated Fair Value, Debt securities 7,455,982 520,063
Debt Securities [Member] | Certificates Of Deposit [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost, Debt securities 1,140,000 127,594
Gross Unrealized Gains 0 41
Gross Unrealized Losses (18) (16)
Estimated Fair Value, Debt securities 1,139,982 127,619
Debt Securities [Member] | U.S. Government Agencies And FDIC Guaranteed Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost, Debt securities 0 1,284,654
Gross Unrealized Gains 0 11,919
Gross Unrealized Losses 0 (463)
Estimated Fair Value, Debt securities 0 1,296,110
Debt Securities [Member] | Municipal Debt Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost, Debt securities 0 17,543
Gross Unrealized Gains 0 103
Gross Unrealized Losses 0 (21)
Estimated Fair Value, Debt securities 0 17,625
Debt Securities [Member] | Non-U.S. Government Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost, Debt securities 55,246 286,410
Gross Unrealized Gains 0 1,880
Gross Unrealized Losses (30,505) (86)
Estimated Fair Value, Debt securities 24,741 288,204
Debt Securities [Member] | Corporate Debt Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost, Debt securities 404,994 985,382
Gross Unrealized Gains 0 7,999
Gross Unrealized Losses (5) (1,746)
Estimated Fair Value, Debt securities 404,989 991,635
Debt Securities [Member] | Residential Mortgage And Asset-Backed Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost, Debt securities 0 277,359
Gross Unrealized Gains 0 923
Gross Unrealized Losses 0 (1,239)
Estimated Fair Value, Debt securities 0 277,043
Debt Securities [Member] | Student Loan-Backed Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost, Debt securities 51,500 75,900
Gross Unrealized Gains 0 0
Gross Unrealized Losses (4,548) (5,129)
Estimated Fair Value, Debt securities $ 46,952 $ 70,771