Note 8 - Loans Disaggregated by Impairment Method (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Credit Losses Related To Financing Receivables Current And Noncurrent [Line Items]
Allowance for loan losses	$ 10,334	$ 9,887	$ 9,015	$ 8,834
Allowance for loan losses - individually evaluated for impairment	3,548	3,566
Allowance for loan losses - collectively evaluated for impairment	6,694	6,065
Loans and leases receivable	821,129	820,419
Loans - individually evaluated for impairment	16,221	16,860
Loans - collectively evaluated for impairment	804,908	803,559
Commercial Portfolio Segment [Member] \| Commercial and Industrial [Member]
Credit Losses Related To Financing Receivables Current And Noncurrent [Line Items]
Allowance for loan losses	4,657	4,689	3,083	3,092
Allowance for loan losses - individually evaluated for impairment	3,143	3,307
Allowance for loan losses - collectively evaluated for impairment	1,514	1,382
Loans and leases receivable	164,071	168,031
Loans - individually evaluated for impairment	5,516	6,027
Loans - collectively evaluated for impairment	158,555	162,004
Commercial Portfolio Segment [Member] \| Construction Loans [Member]
Credit Losses Related To Financing Receivables Current And Noncurrent [Line Items]
Allowance for loan losses	286	590	602	551
Allowance for loan losses - individually evaluated for impairment	0	0
Allowance for loan losses - collectively evaluated for impairment	286	590
Loans and leases receivable	47,634	56,209
Loans - collectively evaluated for impairment	47,634	56,209
Commercial Portfolio Segment [Member] \| Secured by Commercial Real Estate [Member]
Credit Losses Related To Financing Receivables Current And Noncurrent [Line Items]
Allowance for loan losses	3,286	2,519	2,829	2,824
Allowance for loan losses - individually evaluated for impairment	358	217
Allowance for loan losses - collectively evaluated for impairment	2,928	2,302
Loans and leases receivable	351,550	336,050
Loans - individually evaluated for impairment	7,061	7,172
Loans - collectively evaluated for impairment	344,489	328,878
Commercial Portfolio Segment [Member] \| Secured by Residential Real Estate [Member]
Credit Losses Related To Financing Receivables Current And Noncurrent [Line Items]
Allowance for loan losses	608	629	743	754
Allowance for loan losses - individually evaluated for impairment	25	31
Allowance for loan losses - collectively evaluated for impairment	583	598
Loans and leases receivable	70,652	72,443
Loans - individually evaluated for impairment	2,003	2,082
Loans - collectively evaluated for impairment	68,649	70,361
State and Political Subdivisions Portfolio Segment [Member]
Credit Losses Related To Financing Receivables Current And Noncurrent [Line Items]
Allowance for loan losses	134	115	190	153
Allowance for loan losses - individually evaluated for impairment	0	0
Allowance for loan losses - collectively evaluated for impairment	134	115
Loans and leases receivable	38,248	38,376
Loans - individually evaluated for impairment	0	0
Loans - collectively evaluated for impairment	38,248	38,376
Retail Portfolio Segment [Member] \| Consumer Loans [Member]
Credit Losses Related To Financing Receivables Current And Noncurrent [Line Items]
Allowance for loan losses	278	230	166	164
Allowance for loan losses - individually evaluated for impairment	9	11
Allowance for loan losses - collectively evaluated for impairment	269	219
Loans and leases receivable	6,232	6,530
Loans - individually evaluated for impairment	67	69
Loans - collectively evaluated for impairment	6,165	6,461
Retail Portfolio Segment [Member] \| Family Residential Mortgages [Member]
Credit Losses Related To Financing Receivables Current And Noncurrent [Line Items]
Allowance for loan losses	660	549	500	497
Allowance for loan losses - collectively evaluated for impairment	660	549
Loans and leases receivable	70,284	69,469
Loans - individually evaluated for impairment	883	955
Loans - collectively evaluated for impairment	69,401	68,514
Retail Portfolio Segment [Member] \| Home Equity Loans and Lines [Member]
Credit Losses Related To Financing Receivables Current And Noncurrent [Line Items]
Allowance for loan losses	333	310	341	338
Allowance for loan losses - individually evaluated for impairment	13	0
Allowance for loan losses - collectively evaluated for impairment	320	310
Loans and leases receivable	72,458	73,311
Loans - individually evaluated for impairment	691	555
Loans - collectively evaluated for impairment	71,767	72,756
Unallocated Financing Receivables [Member]
Credit Losses Related To Financing Receivables Current And Noncurrent [Line Items]
Allowance for loan losses	$ 92	$ 256	$ 561	$ 461

Credit losses related to financing receivables current and noncurrent.

No definition available.

Name:	qnbc_CreditLossesRelatedToFinancingReceivablesCurrentAndNoncurrentLineItems
Namespace Prefix:	qnbc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

+ Details

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

- Definition

The balance of financing receivables that were individually evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

+ Details

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

- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=118939070&loc=d3e15032-111544

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 6.L.1)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

+ Details

Name:	us-gaap_LoansAndLeasesReceivableAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118952595&loc=d3e4428-111522

+ Details

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

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=qnbc_CommercialAndIndustrialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=qnbc_SecuredByCommercialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=qnbc_SecuredByResidentialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=qnbc_StateAndPoliticalSubdivisionsPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=qnbc_RetailPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ConsumerLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=qnbc_FamilyResidentialMortgagesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=qnbc_HomeEquityLoansAndLinesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_UnallocatedFinancingReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: