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Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk - Commitments (Details) - USD ($) $ in Thousands | Jun. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Company's contractual commitments due to letters of credit |  |
Total letters of credit | $ 15,389 | $ 12,278
Fixed |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 2,931 | 418
Variable |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 12,458 | 11,860
Borrower |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 15,322 | 12,136
Borrower | Fixed |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 2,931 | 418
Borrower | Variable |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 12,391 | 11,718
Borrower | Financial standby |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 7,337 | 3,947
Borrower | Financial standby | Fixed |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 2,017 | 177
Borrower | Financial standby | Variable |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 5,320 | 3,770
Borrower | Commercial standby |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 395 | 354
Borrower | Commercial standby | Variable |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 395 | 354
Borrower | Performance standby |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 7,590 | 7,835
Borrower | Performance standby | Fixed |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 914 | 241
Borrower | Performance standby | Variable |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 6,676 | 7,594
Nonborrower | Performance standby |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 67 | 142
Nonborrower | Performance standby | Variable |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | $ 67 | $ 142

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