XML 22 R1.htm IDEA: XBRL DOCUMENT v3.25.0.1
Document And Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2024
Feb. 25, 2025
Jun. 30, 2024
Document Information [Line Items]      
Entity Central Index Key 0001274173    
Entity Registrant Name JANUS HENDERSON GROUP PLC    
Amendment Flag false    
Current Fiscal Year End Date --12-31    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2024    
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2024    
Document Transition Report false    
Entity File Number 001-38103    
Entity Incorporation, State or Country Code Y9    
Entity Tax Identification Number 98-1376360    
Entity Address, Address Line One 201 Bishopsgate    
Entity Address, City or Town London    
Entity Address, Country GB    
Entity Address, Postal Zip Code EC2M3AE    
City Area Code 44    
Local Phone Number (0) 20 7818 1818    
Title of 12(b) Security Common Stock, $1.50 Per Share Par Value    
Trading Symbol JHG    
Security Exchange Name NYSE    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 5,381,586,868.43
Entity Common Stock, Shares Outstanding   157,557,812  
Auditor Firm ID 238    
Auditor Name PricewaterhouseCoopers LLP    
Auditor Location Denver, Colorado