Note 6 - Loans Receivable, Net and Allowance for Loan Losses - Changes in the Allowance for Loan Losses and Recorded Investment in Loans Receivable (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Allowance for loan losses, beginning balance	$ 2,651	$ 2,126	$ 2,231	$ 1,965	$ 1,965
Charge-offs					(37)
Recoveries
Provision	201	157	621	318	303
Ending balance	2,852	2,283	2,852	2,283	2,231
Allowance for loan losses, individually evaluated for impairment	3	54	3	54	4
Allowance for loan losses, collectively evaluated for impairment	2,852	2,229	2,852	2,229	2,227
Loans	350,867		350,867		249,767
Loans receivable, individually evaluated for impairment	321		321		323
Loans receivable, collectively evaluated for impairment	350,546		350,546		249,444
Real Estate Portfolio Segment [Member]
Loans	209,651		209,651		204,000
Real Estate Portfolio Segment [Member] \| One-to-four Family Residential Owner Occupied Loans [Member]
Allowance for loan losses, beginning balance	43	49	52	51	51
Charge-offs
Recoveries
Provision	4	(1)	(5)	(3)	1
Ending balance	47	48	47	48	52
Allowance for loan losses, individually evaluated for impairment
Allowance for loan losses, collectively evaluated for impairment	47	48	47	48	52
Loans	5,385		5,385		6,298
Loans receivable, individually evaluated for impairment	171		171		172
Loans receivable, collectively evaluated for impairment	5,214		5,214		6,126
Real Estate Portfolio Segment [Member] \| One-to-four Family Residential Non-owner Occupied Loans [Member]
Allowance for loan losses, beginning balance	399	437	351	435	435
Charge-offs					(37)
Recoveries
Provision	9	(20)	57	(18)	(47)
Ending balance	408	417	408	417	351
Allowance for loan losses, individually evaluated for impairment		50		50
Allowance for loan losses, collectively evaluated for impairment	408	367	408	367	351
Loans	40,872		40,872		39,897
Loans receivable, individually evaluated for impairment	19		19		19
Loans receivable, collectively evaluated for impairment	40,853		40,853		39,878
Real Estate Portfolio Segment [Member] \| Multi-family (Five Or More) Residential Loans [Member]
Allowance for loan losses, beginning balance	204	153	145	156	156
Charge-offs
Recoveries
Provision	47	(3)	106	(6)	(11)
Ending balance	251	150	251	150	145
Allowance for loan losses, individually evaluated for impairment
Allowance for loan losses, collectively evaluated for impairment	251	150	251	150	145
Loans	22,814		22,814		22,233
Loans receivable, individually evaluated for impairment
Loans receivable, collectively evaluated for impairment	22,814		22,814		22,233
Real Estate Portfolio Segment [Member] \| Commercial Real Estate and Lines of Credit [Member]
Allowance for loan losses, beginning balance	1,229	835	854	839	839
Charge-offs
Recoveries
Provision	93		468	(4)	15
Ending balance	1,322	835	1,322	835	854
Allowance for loan losses, individually evaluated for impairment		4		4	4
Allowance for loan losses, collectively evaluated for impairment	1,322	831	1,322	831	850
Loans	128,965		128,965		119,323
Loans receivable, individually evaluated for impairment	131		131		132
Loans receivable, collectively evaluated for impairment	128,834		128,834		119,191
Real Estate Portfolio Segment [Member] \| Construction Loans [Member]
Allowance for loan losses, beginning balance	114	180	250	175	175
Charge-offs
Recoveries
Provision	(1)	89	(137)	94	75
Ending balance	113	269	113	269	250
Allowance for loan losses, individually evaluated for impairment
Allowance for loan losses, collectively evaluated for impairment	113	269	113	269	250
Loans	7,512		7,512		12,523
Loans receivable, individually evaluated for impairment
Loans receivable, collectively evaluated for impairment	7,512		7,512		12,523
Real Estate Portfolio Segment [Member] \| Home Equity Loan [Member]
Allowance for loan losses, beginning balance	25	23	19	21	21
Charge-offs
Recoveries
Provision	2	(3)	8	(1)	(2)
Ending balance	27	20	27	20	19
Allowance for loan losses, individually evaluated for impairment
Allowance for loan losses, collectively evaluated for impairment	27	20	27	20	19
Loans	4,103		4,103		3,726
Loans receivable, individually evaluated for impairment
Loans receivable, collectively evaluated for impairment	4,103		4,103		3,726
Commercial and Consumer Portfolio Segments [Member]
Allowance for loan losses, beginning balance	537	370	500	247	247
Charge-offs
Recoveries
Provision	(53)	74	(16)	197	253
Ending balance	484	444	484	444	500
Allowance for loan losses, individually evaluated for impairment
Allowance for loan losses, collectively evaluated for impairment	484	444	484	444	500
Loans	141,216		141,216		45,767
Loans receivable, individually evaluated for impairment
Loans receivable, collectively evaluated for impairment	141,216		141,216		45,767
Unallocated Financing Receivables [Member]
Allowance for loan losses, beginning balance	100	79	60	41	41
Charge-offs
Recoveries
Provision	100	21	140	59	19
Ending balance	200	100	200	100	60
Allowance for loan losses, individually evaluated for impairment
Allowance for loan losses, collectively evaluated for impairment	200	$ 100	200	$ 100	60
Loans
Loans receivable, individually evaluated for impairment
Loans receivable, collectively evaluated for impairment

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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 (c)(1)
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(7)(2))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121599878&loc=SL82895884-210446

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447

+ Details

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

- Definition

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

+ References

+ 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

Amount of increase in allowance for credit loss on financing receivable from recovery.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 79
-URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922352-210448

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(4)
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of writeoff of financing receivable, charged against allowance for credit loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447

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 (c)(3)
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 79
-URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922352-210448

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

+ 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

+ Details

Name:	us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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=121593590&loc=d3e4428-111522

+ Details

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

- Definition

Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

+ References

+ Details

Name:	us-gaap_ProvisionForLoanLeaseAndOtherLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=qnto_CommercialAndConsumerPortfolioSegmentsMember
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: