Fair value estimates - Additional Quantitative Information about Assets Measured at Fair Value on Nonrecurring Basis (Details) - Level 3 - Nonrecurring Basis - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Other Real Estate Owned
Fair Value Inputs, Assets, Quantitative Information
Assets, Fair Value Estimate	$ 236	$ 371
Range and weighted average of appraisal adjustments	34.90%	43.10%
Range and weighted average of liquidation expenses	5.00%	5.00%
Other Real Estate Owned \| Minimum
Fair Value Inputs, Assets, Quantitative Information
Range and weighted average of appraisal adjustments	20.00%	25.00%
Range and weighted average of liquidation expenses	3.00%	3.00%
Other Real Estate Owned \| Maximum
Fair Value Inputs, Assets, Quantitative Information
Range and weighted average of appraisal adjustments	40.00%	54.60%
Range and weighted average of liquidation expenses	6.00%	6.00%
Impaired Loans
Fair Value Inputs, Assets, Quantitative Information
Assets, Fair Value Estimate	$ 2,474	$ 3,193
Range and weighted average of appraisal adjustments	63.00%	74.50%
Range and weighted average of liquidation expenses	4.90%	5.30%
Impaired Loans \| Minimum
Fair Value Inputs, Assets, Quantitative Information
Range and weighted average of appraisal adjustments	3.70%	18.00%
Range and weighted average of liquidation expenses	3.00%	3.00%
Impaired Loans \| Maximum
Fair Value Inputs, Assets, Quantitative Information
Range and weighted average of appraisal adjustments	97.00%	97.00%
Range and weighted average of liquidation expenses	6.00%	6.00%

Represents the range and weighted average of appraisal adjustments presented as a percent of the appraisal.

No definition available.

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- Definition

Represents the range and weighted average of liquidation expenses presented as a percent of the appraisal.

+ References

No definition available.

+ Details

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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