Investment Securities - Additonal disclosures - (Details) - USD ($)	3 Months Ended	12 Months Ended
Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2016
Additional disclosures
Total Other than Temporary Impairments on Securities	$ 489,000	$ 489,000
Carrying value of investment securities pledged to secure public funds deposits and for other purposes required and permitted by law	307,400,000	307,400,000	$ 295,200,000
Carrying amount of the securities pledged to collateralize repurchase agreements	$ 219,900,000	$ 219,900,000	$ 238,300,000

The carrying amount as of the date of the latest financial statement presented of securities which are owned but transferred to serve as collateral for repurchase agreements, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729

Name:	us-gaap_PledgedFinancialInstrumentsNotSeparatelyReportedSecuritiesForRepurchaseAgreements
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant