Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions - Interest Rate Derivatives (Details) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017 USD ($) item	Dec. 31, 2016 USD ($) item
Not designated
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Asset Derivatives, Fair Value	$ 704	$ 960
Liability Derivatives, Fair Value	385	673
Interest rate swap agreements net of swap credit valuation | Cash Flow Hedging [Member]
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Unrealized loss	(1,458)	(994)
Notional or Contractual Amount	25,774	25,774
Interest rate swap agreements net of swap credit valuation | Not designated
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Investment securities pledged with financial institutions, dollars	$ 4,200	$ 6,200
Number of correspondent financial institutions where investment securities are pledged | item	2	2
Weighted average maturity	7 years 2 months 12 days	7 years 3 months 18 days
Notional or Contractual Amount	$ 101,613	$ 85,807
Asset Derivatives, Fair Value	385	673
Liability Derivatives, Fair Value	385	673
Commitments | Not designated
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Notional or Contractual Amount	37,142	31,980
Asset Derivatives, Fair Value	$ 319	$ 287