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Interest-Rate Swaps (Details) - USD ($) $ in Thousands | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2017 | Dec. 31, 2016
Derivative [Line Items] |  |
Weighted average pay rate on interest-rate swaps | 4.45% | 4.34%
Weighted average receive rate on interest-rate swaps | 3.59% | 3.04%
Weighted average maturity (years) | 3 years 3 months 19 days | 4 years 9 months 18 days
Fair value of combined interest-rate swaps | $ 723 | $ 685
Interest rate swaps |  |
Derivative [Line Items] |  |
Notional amounts | $ 39,868 | $ 34,360

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