Borrowings and Borrowing Capacity - Summary of Junior Subordinated Debentures (Details) - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Face Value	$ 51,031,000
Carrying Value	38,623,000	$ 32,740,000
National Bancshares Capital Trusts II
Debt Instrument [Line Items]
Face Value	15,464,000
Carrying Value	$ 12,861,000
Maturity Date	2033-09
National Bancshares Capital Trusts II \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest Rate, Description	LIBOR + 3.00%
Interest Rate	4.59%
National Bancshares Capital Trusts III
Debt Instrument [Line Items]
Face Value	$ 17,526,000
Carrying Value	$ 12,389,000
Maturity Date	2036-07
National Bancshares Capital Trusts III \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest Rate, Description	LIBOR + 1.64%
Interest Rate	3.00%
ColoEast Capital Trust I
Debt Instrument [Line Items]
Face Value	$ 5,155,000
Carrying Value	$ 3,417,000
Maturity Date	2035-09
ColoEast Capital Trust I \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest Rate, Description	LIBOR + 1.60%
Interest Rate	3.29%
ColoEast Capital Trust II
Debt Instrument [Line Items]
Face Value	$ 6,700,000
Carrying Value	$ 4,485,000
Maturity Date	2037-03
ColoEast Capital Trust II \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest Rate, Description	LIBOR + 1.79%
Interest Rate	3.48%
Valley Bancorp Statutory Trust I
Debt Instrument [Line Items]
Face Value	$ 3,093,000
Carrying Value	$ 2,844,000
Maturity Date	2032-09
Valley Bancorp Statutory Trust I \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest Rate, Description	LIBOR + 3.40%
Interest Rate	5.07%
Valley Bancorp Statutory Trust II
Debt Instrument [Line Items]
Face Value	$ 3,093,000
Carrying Value	$ 2,627,000
Maturity Date	2034-07
Valley Bancorp Statutory Trust II \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest Rate, Description	LIBOR + 2.75%
Interest Rate	4.35%

Date instrument maturity date month and year.

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- Definition

Including the current and noncurrent portions, the face value of junior subordinated long-term debt owed to unconsolidated subsidiary trusts as of the balance sheet date.

+ References

No definition available.

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Including the current and noncurrent portions, the carrying value of junior subordinated long-term debt owed to unconsolidated subsidiary trusts as of the balance sheet date. Such debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets and was initially scheduled to be repaid after one year or beyond the normal operating cycle if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

Description of the interest rate for the amounts borrowed under the credit facility, including the terms and the method for determining the interest rate (for example, fixed or variable, LIBOR plus a percentage, increasing rate, timing of interest rate resets, remarketing provisions).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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