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Short-term borrowings (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary of securities sold under agreements to repurchase
Average balance during the year	$ 82,627	$ 84,368	$ 71,779
Average interest rate during the year	0.13%	0.07%	0.07%
Maximum month-end balance during the year	$ 94,208	$ 98,687	$ 89,574
Weighted average year-end interest rate	0.14%	0.08%	0.06%
Balance at year-end	$ 74,215	$ 78,110	$ 75,482

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Assets sold under agreements to repurchase average during year.

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Assets sold under agreements to repurchase average interest rate during year.

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Assets sold under agreements to repurchase maximum month end during year.

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- Definition

Assets sold under agreements to repurchase weighted average year end interest rate.

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Summary of securities sold under agreements to repurchase.

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Carrying amount of assets sold under agreements to repurchase when the carrying amount (or market value, if higher than the carrying amount) of securities or other assets sold under repurchase agreements exceeds 10 percent of total assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(m)(1)(i)(A)(i))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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