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Commitments and Contingencies - Commitments and Letters of Credit (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016
Commitment And Contingencies [Line Items] |  |
Total Commitments | $ 1,501,346 | $ 1,594,230
Standby letters of credit |  |
Commitment And Contingencies [Line Items] |  |
Total Commitments | 80,918 | 84,534
Commitments to extend credit |  |
Commitment And Contingencies [Line Items] |  |
Total Commitments | $ 1,420,428 | $ 1,509,696

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- Definition Commitment And Contingencies [Line Items] + References No definition available. + Details
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- Definition Maximum amount of loss due to credit risk that, based on the gross fair value of the financial instrument, the entity would incur if parties to the financial instruments that make up the concentration failed completely to perform according to the terms of the contracts and the collateral or other security, if any, for the amount due proved to be of no value to the entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13537-108611 + Details
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