Disclosures of Fair Values of Financial Instruments, Part II (Details) - USD ($)		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Foreclosed Assets Held for Sale [Abstract]
Other real estate owned		$ 2,754,000	$ 1,982,000
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Assets, Fair Value Disclosure, Recurring		2,548,000	1,652,000
Financial Assets [Abstract]
Available-for-sale securities		578,579,000	619,848,000
Held-to-maturity Securities		69,332,000	74,231,000
Held-to-maturity Securities, Fair Value		68,457,000	73,096,000
Other borrowings		10,313,000	18,063,000
Carrying Amount
Financial Assets [Abstract]
Cash and due from banks		88,388,000	137,002,000
Federal funds sold		491,000	38,900,000
Certificates of deposit investments		1,685,000	14,643,000
Available-for-sale securities		578,579,000	619,848,000
Held-to-maturity Securities		69,332,000
Held-to-maturity Securities, Fair Value			74,231,000
Loans held for sale		1,025,000	1,175,000
Loans net of allowance for loan losses		1,918,499,000	1,808,064,000
Interest receivable		10,832,000	10,553,000
Federal Reserve Bank stock		5,160,000	3,949,000
Federal Home Loan Bank stock		2,407,000	4,389,000
Deposits		2,274,639,000	2,329,887,000
Securities sold under agreements to repurchase		155,388,000	185,763,000
Interest payable		602,000	535,000
Federal Home Loan Bank borrowings		60,038,000	40,094,000
Other borrowings		10,313,000
Junior subordinated debentures		24,000,000	23,917,000
Fair Value
Financial Assets [Abstract]
Cash and due from banks		88,388,000	137,002,000
Federal funds sold		491,000	38,900,000
Certificates of deposit investments		1,692,000	14,651,000
Available-for-sale securities		578,579,000	619,848,000
Held-to-maturity Securities, Fair Value		68,457,000	73,096,000
Loans held for sale		1,025,000	1,175,000
Loans net of allowance for loan losses		1,899,678,000	1,795,764,000
Interest receivable		10,832,000	10,553,000
Federal Reserve Bank stock		5,160,000	3,949,000
Federal Home Loan Bank stock		2,407,000	4,389,000
Deposits		2,272,868,000	2,331,725,000
Securities sold under agreements to repurchase		155,394,000	185,766,000
Interest payable		602,000	535,000
Federal Home Loan Bank borrowings		59,968,000	40,318,000
Other borrowings		10,313,000
Junior subordinated debentures		18,050,000	17,068,000
Fair Value, Measurements, Nonrecurring [Member] | Carrying Amount
Foreclosed Assets Held for Sale [Abstract]
Other real estate owned		2,754,000	1,982,000
Fair Value, Measurements, Nonrecurring [Member] | Fair Value
Foreclosed Assets Held for Sale [Abstract]
Other real estate owned		91,000	173,000
Fair Value, Inputs, Level 1 [Member]
Financial Assets [Abstract]
Cash and due from banks		88,388,000	137,002,000
Federal funds sold		491,000	38,900,000
Certificates of deposit investments		0	0
Available-for-sale securities		172,000	144,000
Loans held for sale		0	0
Loans net of allowance for loan losses		0	0
Interest receivable		0	0
Federal Reserve Bank stock		0	0
Federal Home Loan Bank stock		0	0
Deposits		0	0
Securities sold under agreements to repurchase		0	0
Interest payable		0	0
Federal Home Loan Bank borrowings		0	0
Other borrowings		0
Junior subordinated debentures		0	0
Fair Value, Inputs, Level 2 [Member]
Financial Assets [Abstract]
Cash and due from banks		0	0
Federal funds sold		0	0
Certificates of deposit investments		1,692,000	14,651,000
Available-for-sale securities		575,859,000	618,052,000
Held-to-maturity Securities, Fair Value		68,457,000	73,096,000
Loans held for sale		1,025,000	1,175,000
Loans net of allowance for loan losses		0	0
Interest receivable		10,832,000	10,553,000
Federal Reserve Bank stock		5,160,000	3,949,000
Federal Home Loan Bank stock		2,407,000	4,389,000
Deposits		1,930,604,000	1,976,806,000
Securities sold under agreements to repurchase		155,394,000	185,766,000
Interest payable		602,000	535,000
Federal Home Loan Bank borrowings		59,968,000	40,318,000
Other borrowings		10,313,000
Junior subordinated debentures		18,050,000	17,068,000
Fair Value, Inputs, Level 3 [Member]
Financial Assets [Abstract]
Cash and due from banks		0	0
Federal funds sold		0	0
Certificates of deposit investments		0	0
Available-for-sale securities		2,548,000	1,652,000
Loans held for sale		0	0
Loans net of allowance for loan losses		1,899,678,000	1,795,764,000
Interest receivable		0	0
Federal Reserve Bank stock		0	0
Federal Home Loan Bank stock		0	0
Deposits		342,264,000	354,919,000
Securities sold under agreements to repurchase		0	0
Interest payable		0	0
Federal Home Loan Bank borrowings		0	0
Other borrowings		0
Junior subordinated debentures		$ 0	$ 0
Trust preferred securities | Fair Value, Inputs, Level 3 [Member] | Discounted Cash Flow [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Constant prepayment rate (in hundredths)	[1]	1.30%	1.30%
Trust preferred securities | Fair Value, Inputs, Level 3 [Member] | Minimum [Member] | Discounted Cash Flow [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount rate (in hundredths)		12.70%	13.60%
Cumulative projected prepayments (in hundredths)		21.60%	22.40%
Probability of default (in hundredths)		0.50%	0.50%
Projected cures given deferral (in hundredths)		0.00%	0.00%
Loss severity		97.70%	97.60%
Trust preferred securities | Fair Value, Inputs, Level 3 [Member] | Maximum [Member] | Discounted Cash Flow [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount rate (in hundredths)
Cumulative projected prepayments (in hundredths)
Probability of default (in hundredths)
Projected cures given deferral (in hundredths)
Loss severity
Trust preferred securities | Fair Value, Inputs, Level 3 [Member] | Weighted Average [Member] | Discounted Cash Flow [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount rate (in hundredths)
Cumulative projected prepayments (in hundredths)
Probability of default (in hundredths)
Projected cures given deferral (in hundredths)
Loss severity
Impaired loans (collateral dependent) | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		$ 3,053,000	$ 6,938,000
Impaired loans (collateral dependent) | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		0	0
Impaired loans (collateral dependent) | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		$ 0	$ 0
Impaired loans (collateral dependent) | Fair Value, Inputs, Level 3 [Member] | Minimum [Member] | Third Party Valuations [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount to reflect realizable value (in hundredths)		0.00%	0.00%
Impaired loans (collateral dependent) | Fair Value, Inputs, Level 3 [Member] | Maximum [Member] | Third Party Valuations [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount to reflect realizable value (in hundredths)		40.00%	40.00%
Impaired loans (collateral dependent) | Fair Value, Inputs, Level 3 [Member] | Weighted Average [Member] | Third Party Valuations [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount to reflect realizable value (in hundredths)		20.00%	20.00%
Impaired loans (collateral dependent) | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		$ 3,053,000	$ 6,938,000
Foreclosed assets held for sale | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		91,000	173,000
Foreclosed assets held for sale | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		0	0
Foreclosed assets held for sale | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		$ 0	$ 0
Foreclosed assets held for sale | Fair Value, Inputs, Level 3 [Member] | Minimum [Member] | Third Party Valuations [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount to reflect realizable value less estimated selling costs (in hundredths)		0.00%	0.00%
Foreclosed assets held for sale | Fair Value, Inputs, Level 3 [Member] | Maximum [Member] | Third Party Valuations [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount to reflect realizable value less estimated selling costs (in hundredths)		40.00%	40.00%
Foreclosed assets held for sale | Fair Value, Inputs, Level 3 [Member] | Weighted Average [Member] | Third Party Valuations [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount to reflect realizable value less estimated selling costs (in hundredths)		35.00%	35.00%
Foreclosed assets held for sale | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		$ 91,000	$ 173,000

[1] Every five years