Business combination last installment payment.

No definition available.

Name:	qnst_BusinessCombinationLastInstallmentPayment
Namespace Prefix:	qnst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Fair value assets Level3 to level1 transfers amount.

+ References

No definition available.

+ Details

Name:	qnst_FairValueAssetsLevel3ToLevel1TransfersAmount
Namespace Prefix:	qnst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value liabilities level3 to level1 transfers amount.

+ References

No definition available.

+ Details

Name:	qnst_FairValueLiabilitiesLevel3ToLevel1TransfersAmount
Namespace Prefix:	qnst_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of assets level1 To level 2 transfers amount.

+ References

No definition available.

+ Details

Name:	qnst_FairValueOfAssetsLevel1ToLevel2TransfersAmount
Namespace Prefix:	qnst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value of assets level 2 to level 1 transfers amount.

+ References

No definition available.

+ Details

Name:	qnst_FairValueOfAssetsLevel2ToLevel1TransfersAmount
Namespace Prefix:	qnst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value of liabilities level 1 to level 2 transfers amount.

+ References

No definition available.

+ Details

Name:	qnst_FairValueOfLiabilitiesLevel1ToLevel2TransfersAmount
Namespace Prefix:	qnst_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of liabilities level 2 to level 1 transfers amount.

+ References

No definition available.

+ Details

Name:	qnst_FairValueOfLiabilitiesLevel2ToLevel1TransfersAmount
Namespace Prefix:	qnst_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of increase (decrease) in value of liability in contingent consideration arrangement in business combination, including, but not limited to, difference arising upon settlement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479581/805-30-50-4

+ Details

Name:	us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

+ Details

Name:	us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=qnst_ModernizeIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=qnst_BestCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2025	Mar. 31, 2026	Mar. 31, 2025	Jun. 30, 2025
Fair Value Liabilities Measured on Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value, assets, level 1 to level 2 transfers, amount		$ 0		$ 0
Fair value, assets, level 2 to level 1 transfers, amount		0		0
Fair value, liabilities, level 1 to level 2 transfers, amount		0		0
Fair value, liabilities, level 2 to level 1 transfers, amount		0		0
Fair value liabilities level 3 to level 1 transfers, amount		0		0
Fair value assets level 3 to level 1 transfers, amount		0		$ 0
Change in the net fair value of contingent consideration		4,650,000	$ 12,394,000
Modernize
Fair Value Liabilities Measured on Recurring Basis Unobservable Input Reconciliation [Line Items]
Business combination last installment payment	$ 5,500,000
BestCompany
Fair Value Liabilities Measured on Recurring Basis Unobservable Input Reconciliation [Line Items]
Business combination last installment payment		$ 2,000,000