Borrowed Funds - Narrative (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) Counterparty	Dec. 31, 2015 USD ($)
Securities sold under agreements to repurchase and other short-term debt disclosures
Variable rate basis	0.72%	0.48%
Advances from Federal Home Loan Banks	$ 106,200,000	$ 132,000,000
FHLB advances, average outstanding balance during the period	82,800,000	61,100,000
Loans collateralized under FHLB advancement agreement	861,000,000	867,400,000
Lending value of loans pledged as collateral for FHLB line of credit	598,500,000	591,200,000
Securities Sold under Agreements to Repurchase
Securities sold under agreements to repurchase and other short-term debt disclosures
Short-term debt, average outstanding amount	46,000,000	57,300,000
Short-term debt, maximum amount outstanding at any month end	$ 71,000,000	$ 68,600,000
Short-term debt, weighted average interest rate	0.07%	0.06%
Revolving Line of Credit (LOC)
Securities sold under agreements to repurchase and other short-term debt disclosures
Maximum borrowing capacity	$ 20,000,000
Commitment fee, percentage	0.35%
Amount outstanding	$ 0	$ 0
Revolving Line of Credit (LOC) | 1-month LIBOR
Securities sold under agreements to repurchase and other short-term debt disclosures
Interest rate terms, spread over reference rate	2.25%
Federal Fund Purchase Lines
Securities sold under agreements to repurchase and other short-term debt disclosures
Short-term debt, average outstanding amount	$ 2,000,000	1,300,000
Maximum borrowing capacity	170,000,000
Amount outstanding	$ 0	$ 0
Number of banks providing line of credit | Counterparty	8