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Note 16 - Retirement Benefit Plans (Details Textual)
$ in Millions
 12 Months Ended
Jan. 01, 2025
Dec. 31, 2024
USD ($)
Dec. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
Number of Plans   2    
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay   5.00%    
Defined Contribution Plan, Employer Matching Contribution, Additional One Time Percent Match   1.00%    
Defined Contribution Plan, Cost   $ 10.1 $ 8.1 $ 8.6
Expected Rate of Return on Plan Assets   4.10%    
Pension Plan [Member]        
Defined Benefit Plan Surplus On Triennial Valuation Of H G P S   $ 2.4    
Defined Benefit Plan, Benefit Obligation, Payment for Settlement   9.6    
Defined Benefit Plan, Plan Assets, Amount   $ 625.1 $ 696.4 660.5
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage   100.00% 100.00%  
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)   $ (11.7) $ 39.6  
Expected Rate of Return on Plan Assets     4.40%  
Defined Benefit Plan, Plan Assets, Contributions by Employer, Excluding Credits to Member's Money Purchase Accounts   2.4    
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year   2.4    
Pension Plan [Member] | JHG-managed Funds [Member]        
Defined Benefit Plan, Plan Assets, Amount   93.9 $ 103.4  
Pension Plan [Member] | Bulk Annuity Policy [Member]        
Defined Benefit Plan, Plan Assets, Amount   217.7 240.7  
Defined Benefit Plan, Change in Financial Condition   (21.9)    
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)   4.2    
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Purchase, Sale, and Settlement   14.5    
Defined Benefit Plan, Interest on Bulk Annuity Asset   9.9    
Defined Benefit Plan Change in Financial Conditions   7.6    
Defined Benefit Plan Change in Demographic Assumptions   0.1    
Foreign Plan [Member]        
Defined Contribution Plan, Contribution Amount   $ 17.3 $ 14.0 $ 15.7
Subsequent Event [Member]        
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay 6.00%