|**Investment Securities (Tables)**                                                                                                                          | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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|**Investments, Debt and Equity Securities [Abstract]**                                                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Analysis of Amortized Cost and Estimated Fair Value of Securities Available for Sale                                                                        | Below is an analysis of the amortized cost and estimated fair values of securities available for sale at:March 31, 2013December 31, 2012AmortizedCostGrossUnrealizedGainsGrossUnrealizedLossesEstimatedFair ValueAmortizedCostGrossUnrealizedGainsGrossUnrealizedLossesEstimatedFair Value(dollars in thousands)Obligations of U.S. Government Agencies:Mortgage-Backed Securities – Residential$26,533$3,929$—$30,462$27,883$3,781$—$31,664Obligations of U.S. Government- Sponsored Enterprises:Mortgage-Backed Securities – Residential969,60023,213(2,153)990,660839,10225,691(392)864,401Mortgage-Backed Securities – Commercial1391—1401481—149Other Government-Sponsored Enterprises241,972579(113)242,438241,970766(72)242,664Obligations of States and Political Subdivisions823—85824—86Corporate Securities6,700303(30)6,9736,703288—6,991Pooled Trust Preferred Collateralized Debt Obligations51,0771(26,566)24,51251,8663(28,496)23,373Total Debt Securities1,296,10328,029(28,862)1,295,2701,167,75430,534(28,960)1,169,328Equities1,820113—1,9331,859116—1,975Total Securities Available for Sale$1,297,923$28,142$(28,862)$1,297,203$1,169,613$30,650$(28,960)$1,171,303
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|                                                                                                                                                            | March 31, 2013                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|                                                                                                                                                            | AmortizedCost                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|                                                                                                                                                            | (dollars in thousands)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Obligations of U.S. Government Agencies:                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Mortgage-Backed Securities – Residential                                                                                                                    | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Obligations of U.S. Government- Sponsored Enterprises:                                                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Mortgage-Backed Securities – Residential                                                                                                                    | 969,600                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Mortgage-Backed Securities – Commercial                                                                                                                     | 139                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Other Government-Sponsored Enterprises                                                                                                                      | 241,972                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Obligations of States and Political Subdivisions                                                                                                            | 82                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Corporate Securities                                                                                                                                        | 6,700                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Pooled Trust Preferred Collateralized Debt Obligations                                                                                                      | 51,077                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Total Debt Securities                                                                                                                                       | 1,296,103                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|Equities                                                                                                                                                    | 1,820                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Total Securities Available for Sale                                                                                                                         | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Amortized Cost and Estimated Fair Value of Debt Securities Available for Sale                                                                               | The amortized cost and estimated fair value of debt securities available for sale atMarch 31, 2013, by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because issuers may have the right to call or repay obligations with or without call or prepayment penalties.AmortizedCostEstimatedFair Value(dollars in thousands)Due within 1 year$25,081$25,332Due after 1 but within 5 years216,972217,191Due after 5 but within 10 years——Due after 10 years57,77831,485299,831274,008Mortgage-Backed Securities (a)996,2721,021,262Total Debt Securities$1,296,103$1,295,270(a)Mortgage Backed Securities include an amortized cost of$26.5 millionand a fair value of$30.5 millionfor Obligations of U.S. Government agencies issued by Ginnie Mae and Obligations of U.S. Government-sponsored enterprises issued by Fannie Mae and Freddie Mac which had an amortized cost of$969.7 millionand a fair value of$990.8 million                                                                                                                                                                                                          
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|                                                                                                                                                            | AmortizedCost                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|                                                                                                                                                            | (dollars in thousands)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Due within 1 year                                                                                                                                           | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Due after 1 but within 5 years                                                                                                                              | 216,972                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Due after 5 but within 10 years                                                                                                                             | —                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Due after 10 years                                                                                                                                          | 57,778                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|                                                                                                                                                            | 299,831                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Mortgage-Backed Securities (a)                                                                                                                              | 996,272                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Total Debt Securities                                                                                                                                       | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
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|(a)                                                                                                                                                         | Mortgage Backed Securities include an amortized cost of$26.5 millionand a fair value of$30.5 millionfor Obligations of U.S. Government agencies issued by Ginnie Mae and Obligations of U.S. Government-sponsored enterprises issued by Fannie Mae and Freddie Mac which had an amortized cost of$969.7 millionand a fair value of$990.8 million                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|Proceeds from Sale, Gross Gains (Losses) Realized on Sales, Maturities and Other-Than-Temporary Impairment Charges Related to Securities Available for Sale | Proceeds from sales, gross gains (losses) realized on sales, maturities and other-than-temporary impairment charges related to securities available for sale were as follows for thethree-months endedMarch 31,:20132012(dollars in thousands)Proceeds from sales$42$—Gross gains (losses) realized:Sales Transactions:Gross gains$4$—Gross losses——4—Maturities and impairmentGross gains——Gross losses——Other-than-temporary impairment————Net gains and impairment$4$—                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
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|                                                                                                                                                            | 2013                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|                                                                                                                                                            | (dollars in thousands)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Proceeds from sales                                                                                                                                         | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Gross gains (losses) realized:                                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Sales Transactions:                                                                                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Gross gains                                                                                                                                                 | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Gross losses                                                                                                                                                | —                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|                                                                                                                                                            | 4                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Maturities and impairment                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
|Gross gains                                                                                                                                                 | —                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Gross losses                                                                                                                                                | —                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Other-than-temporary impairment                                                                                                                             | —                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|                                                                                                                                                            | —                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Net gains and impairment                                                                                                                                    | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        

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                    duration X- DefinitionTabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.+ ReferencesReference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27290-111563Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27198-111563Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Emerging Issues Task Force (EITF) -Number 03-1 -Paragraph 21 -Subparagraph a, b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 320 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS115-1/124-1 -Paragraph 17 -Subparagraph a, b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27337-111563Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19, 20, 21 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27161-111563Reference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 320 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62586-112803Reference 10: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27357-111563+ Details**Name:**
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