Fair Value (Schedule Of Financial Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value	$ 4,604,835	$ 1,488,885
Derivative financial instruments - assets		2,952
Other short-term investments		274,974
Total assets	4,618,995	1,766,811
Derivative financial instruments - liabilities		2,952
Total Liabilities	14,995	2,952
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments - assets
Other short-term investments		274,974
Total assets	283,245	411,679
Derivative financial instruments - liabilities
Total Liabilities
Level 1 [Member] | Debt Securities Issued By The U.S. Treasury And Other Government Corporations And Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value	260,590	117,435
Level 1 [Member] | Debt Securities Issued By States Of The United [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value
Level 1 [Member] | Debt Securities Issued By States Of The United States And Political Subdivisions Of The States [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value
Level 1 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value	17,606	15,285
Level 1 [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value
Level 1 [Member] | Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value
Level 1 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value	5,049	3,985
Level 1 [Member] | Derivative Financial Instruments, Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments - assets
Level 1 [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments - liabilities
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments - assets		2,952
Other short-term investments
Total assets	4,335,750	1,355,132
Derivative financial instruments - liabilities		2,952
Total Liabilities	14,995	2,952
Level 2 [Member] | Debt Securities Issued By The U.S. Treasury And Other Government Corporations And Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value
Level 2 [Member] | Debt Securities Issued By States Of The United [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value		180,443
Level 2 [Member] | Debt Securities Issued By States Of The United States And Political Subdivisions Of The States [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value	314,304
Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value
Level 2 [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value	2,548,618	799,686
Level 2 [Member] | Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value	1,458,668	372,051
Level 2 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value
Level 2 [Member] | Derivative Financial Instruments, Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments - assets	14,160
Level 2 [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments - liabilities	14,995
Debt Securities Issued By The U.S. Treasury And Other Government Corporations And Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value	260,590	117,435
Debt Securities Issued By States Of The United [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value		180,443
Debt Securities Issued By States Of The United States And Political Subdivisions Of The States [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value	314,304
Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value	17,606	15,285
Residential Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value	2,548,618	799,686
Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value	1,458,668	372,051
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities, Fair Value	5,049	3,985
Derivative Financial Instruments, Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments - assets	14,160
Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments - liabilities	$ 14,995