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Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions - Commitments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Company's contractual commitments due to letters of credit
Total letters of credit	$ 12,447	$ 13,511
Fixed
Company's contractual commitments due to letters of credit
Total letters of credit	243	315
Variable
Company's contractual commitments due to letters of credit
Total letters of credit	12,204	13,196
Borrower
Company's contractual commitments due to letters of credit
Total letters of credit	12,025	12,891
Borrower | Fixed
Company's contractual commitments due to letters of credit
Total letters of credit	243	220
Borrower | Variable
Company's contractual commitments due to letters of credit
Total letters of credit	11,782	12,671
Borrower | Financial standby
Company's contractual commitments due to letters of credit
Total letters of credit	3,925	4,184
Borrower | Financial standby | Fixed
Company's contractual commitments due to letters of credit
Total letters of credit	177	137
Borrower | Financial standby | Variable
Company's contractual commitments due to letters of credit
Total letters of credit	3,748	4,047
Borrower | Commercial standby
Company's contractual commitments due to letters of credit
Total letters of credit	122	126
Borrower | Commercial standby | Variable
Company's contractual commitments due to letters of credit
Total letters of credit	122	126
Borrower | Performance standby
Company's contractual commitments due to letters of credit
Total letters of credit	7,978	8,581
Borrower | Performance standby | Fixed
Company's contractual commitments due to letters of credit
Total letters of credit	66	83
Borrower | Performance standby | Variable
Company's contractual commitments due to letters of credit
Total letters of credit	7,912	8,498
Nonborrower | Performance standby
Company's contractual commitments due to letters of credit
Total letters of credit	422	620
Nonborrower | Performance standby | Fixed
Company's contractual commitments due to letters of credit
Total letters of credit		95
Nonborrower | Performance standby | Variable
Company's contractual commitments due to letters of credit
Total letters of credit	$ 422	$ 525

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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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