| **Short-term Borrowings**      | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
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| **Short-term Debt [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| Short-term Borrowings          | Short-term BorrowingsShort-term borrowings at December 31 were as follows: 2014 2013 2012 EndingBalance AverageBalance AverageRate EndingBalance AverageBalance AverageRate EndingBalance AverageBalance AverageRate (dollars in thousands)Federal funds purchased$9,000 $11,691 0.36% $16,000 $11,982 0.36% $34,000 $47,727 0.27%Borrowings from FHLB945,000 644,651 0.31 478,100 335,449 0.27 178,100 214,703 0.25Securities sold under agreements to repurchase151,876 159,051 0.24 132,515 130,957 0.25 144,127 139,766 0.28Total$1,105,876 $815,393 0.30 $626,615 $478,388 0.26 $356,227 $402,196 0.27Maximum total at any month-end$1,105,876     $626,615     $486,144    Weighted average rate at year-end    0.30%     0.27%     0.25%Interest expense on short-term borrowings for the years ended December 31 is detailed below: 2014 2013 2012 (dollars in thousands)Federal funds purchased$42 $43 $128Borrowings from FHLB2,019 893 545Securities sold under agreements to repurchase388 326 397Total interest on short-term borrowings$2,449 $1,262 $1,070 |

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| - Definition
The entire disclosure for short-term debt.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Article 5Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 7Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.16) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.13) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 13 -Article 9
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