Name:	jhg_EBPAssetHeldForInvestmentParticipantLoanVariableRatePrime
Namespace Prefix:	jhg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of employer matching contribution on qualified student loan payments in eligible participant contribution to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

No definition available.

Name:	jhg_EBPEmployerContributionMatchingPercentageOnQualifiedStudentLoanPayments
Namespace Prefix:	jhg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of participant qualified student loan payments eligible for employer matching contribution for participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

No definition available.

Name:	jhg_EBPEmployerContributionParticipantCompensationMatchedQualifiedStudentLoanPaymentsPercentage
Namespace Prefix:	jhg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Minimum age of participant required to take in service distribution in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

No definition available.

Name:	jhg_EBPMinimumAgeOfParticipantToTakeInServiceDistribution
Namespace Prefix:	jhg_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

The required age of participant to make Secure Act 2.0 contributions to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

No definition available.

Name:	jhg_EBPParticipantAgeForSecureActContributions
Namespace Prefix:	jhg_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

Percentage of participant balance in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) eligible to be transferred into participant-directed investments.

No definition available.

Name:	jhg_EBPParticipantBalanceEligibleForTransferToParticipantdirectedInvestments
Namespace Prefix:	jhg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of maximum after-tax annual compensation that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), is permitted to contribute to total pretax annual compensation.

No definition available.

Name:	jhg_EBPParticipantContributionPretaxMaximumAnnualCompensationToTotalCompensationAftertaxPercentage
Namespace Prefix:	jhg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

IRS limit of maximum amount of catch-up contribution that is permitted to contribute to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

No definition available.

Name:	jhg_EBPParticipantMaximumCatchupContributionIRSLimit
Namespace Prefix:	jhg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Secure Act limit of maximum amount of catch-up contribution that is permitted to contribute to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

No definition available.

Name:	jhg_EBPParticipantMaximumCatchupContributionSecureAct
Namespace Prefix:	jhg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The minimum age of participant to make voluntary catch-up contributions to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

No definition available.

Name:	jhg_EBPParticipantMinimumAgeForCatchupDeferralContributions
Namespace Prefix:	jhg_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

The vesting percentage in an employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) upon reaching retirement age, elimination, disability, or death.

No definition available.

Name:	jhg_EBPParticipantPercentageVestedUponRetirementAgeEliminationDisabilityOrDeath
Namespace Prefix:	jhg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The percentage of participant self contributions that are vested in an employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

No definition available.

Name:	jhg_EBPParticipantSelfContributionsVestedPercentage
Namespace Prefix:	jhg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The number of years of service required for a participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) to transfer funds into participant-directed investments.

No definition available.

Name:	jhg_EBPParticipantYearsOfServiceEligibleForTransferIntoParticipantdirectedInvestments
Namespace Prefix:	jhg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The standard years of service required for participants employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) to achieve full vesting.

No definition available.

Name:	jhg_EBPParticipantYearsOfServiceUntilFullVestingPercentage
Namespace Prefix:	jhg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Vesting percentage in accounts in case of employee benefit plan (EBP) plan termination.

No definition available.

Name:	jhg_EBPTerminationOfPlanVestedPercentage
Namespace Prefix:	jhg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Amount of vested balance at termination to cash out in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

No definition available.

Name:	jhg_EBPTerminationVestedBalanceToCashOut
Namespace Prefix:	jhg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of vested balance at termination in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) to roll account.

No definition available.

Name:	jhg_EBPTerminationVestedBalanceToRollAccount
Namespace Prefix:	jhg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Percentage of employer matching contribution on eligible participant contribution to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

Name:	us-gaap-ebp_EmployeeBenefitPlanEmployerContributionMatchingPercentage
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of participant compensation eligible for employer matching contribution for participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

Name:	us-gaap-ebp_EmployeeBenefitPlanEmployerContributionParticipantCompensationMatchedPercentage
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Amount of plan asset, in forfeited nonvested account, no longer allocated to participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

Name:	us-gaap-ebp_EmployeeBenefitPlanForfeitedNonvestedAccount
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of decrease in forfeited nonvested account of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) from administrative expense.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (j)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478416/962-205-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-04(5)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Name:	us-gaap-ebp_EmployeeBenefitPlanForfeitedNonvestedAccountDecreaseForAdministrativeExpense
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of decrease in forfeited nonvested account of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) from employer contribution.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 962
-SubTopic 325
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478873/962-325-55-17

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (j)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478416/962-205-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-04(5)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Name:	us-gaap-ebp_EmployeeBenefitPlanForfeitedNonvestedAccountDecreaseForEmployerContribution
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of maximum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow.

Name:	us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMaximumBorrowingAmount
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Percentage of maximum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow to total participant account balance.

Name:	us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMaximumBorrowingToTotalAccountPercentage
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Percentage of maximum pretax annual compensation that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), is permitted to contribute to total pretax annual compensation.