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Short-term borrowings (Parenthetical) (Details) - Pledged	Dec. 31, 2017	Dec. 31, 2016
Repurchase advance
Assets Sold Under Agreements To Repurchase [Line Items]
Federal Home Loan Bank interest rate	0.59%	1.48%
Fixed rate advances | Minimum
Assets Sold Under Agreements To Repurchase [Line Items]
Federal Home Loan Bank interest rate	1.43%
Fixed rate advances | Maximum
Assets Sold Under Agreements To Repurchase [Line Items]
Federal Home Loan Bank interest rate	1.49%
Cash management advance
Assets Sold Under Agreements To Repurchase [Line Items]
Federal Home Loan Bank interest rate	0.00%	0.59%

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- Definition

Discloses the single interest rate [if] applicable to the advances from the Federal Home Loan Bank, by branch, as of the Balance Sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

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