v3.26.1
Fair Value Measurements (Assets and Liabilities Measured on a Recurring Basis) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Mar. 31, 2026
Dec. 31, 2025
Mar. 31, 2025
Dec. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]                
Investments, Fair Value Disclosure $ 821.4 $ 833.7 $ 821.4 $ 833.7   $ 844.0   $ 742.0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]                
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]                
Investments, Fair Value Disclosure 42.8   42.8     48.2    
Derivative Asset, Fair Value, Gross Asset 0.0   0.0     0.0    
Loans Receivable, Fair Value Disclosure 0.0   0.0     0.0    
Deferred compensation plan assets 0.0   0.0     0.0    
Mortgage banking derivative asset 0.0   0.0     0.0    
Total assets at fair value 42.8   42.8     48.2    
Derivative Liability, Fair Value, Gross Liability 0.0   0.0     0.0    
Deferred compensation plan liabilities 0.0   0.0     0.0    
Business Combination, Contingent Consideration, Liability 0.0   0.0     0.0    
Mortgage banking derivative liabilities 0.0   0.0     0.0    
Total liabilities at fair value 0.0   0.0     0.0    
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]                
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]                
Investments, Fair Value Disclosure 0.0   0.0     0.0    
Derivative Asset, Fair Value, Gross Asset 14.8   14.8     5.8    
Loans Receivable, Fair Value Disclosure 700.3   700.3     751.2    
Deferred compensation plan assets 797.2   797.2     723.6    
Mortgage banking derivative asset 0.0   0.0     0.0    
Total assets at fair value 1,512.3   1,512.3     1,480.6    
Derivative Liability, Fair Value, Gross Liability 14.9   14.9     14.2    
Deferred compensation plan liabilities 786.6   786.6     731.4    
Business Combination, Contingent Consideration, Liability 0.0   0.0     0.0    
Mortgage banking derivative liabilities 0.0   0.0     0.0    
Total liabilities at fair value 801.5   801.5     745.6    
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]                
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]                
Derivative Assets (Liabilities), at Fair Value, Net 25.8 19.9 25.8 19.9 $ 46.6 31.6 $ 16.7 93.8
Investments, Fair Value Disclosure 295.6 293.1 295.6 293.1 305.7 304.7 311.0 330.3
Derivative Asset, Fair Value, Gross Asset 0.0   0.0     0.0    
Loans Receivable, Fair Value Disclosure 0.0   0.0     0.0    
Deferred compensation plan assets 0.0   0.0     0.0    
Mortgage banking derivative asset 51.1   51.1     52.2    
Total assets at fair value 346.7   346.7     356.9    
Derivative Liability, Fair Value, Gross Liability 0.0   0.0     0.0    
Deferred compensation plan liabilities 0.0   0.0     0.0    
Business Combination, Contingent Consideration, Liability 17.0 19.1 17.0 19.1 $ 17.7 17.2 $ 37.5 $ 35.8
Mortgage banking derivative liabilities 25.3   25.3     20.6    
Total liabilities at fair value 42.3   42.3     $ 37.8    
Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]                
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]                
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings (10.2) (25.3) (8.5) (45.2)        
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) 0.1 1.4 (0.6) 2.1        
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases 0.0 6.0 0.0 6.0        
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements 0.0 0.0 0.0 (0.1)        
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 0.0 0.0 0.0 0.0        
Derivative [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]                
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]                
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings 13.6 9.7 51.1 17.0        
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) 0.0 0.0 0.0 0.0        
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases 31.2 34.9 65.9 64.9        
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements (65.6) (41.4) (122.8) (155.8)        
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 0.0 0.0 0.0 0.0        
Earn-out Liabilities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]                
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]                
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings 0.0 (7.4) 0.5 (3.5)        
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) 0.0 0.3 0.0 0.4        
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases 0.0 0.2 0.0 0.2        
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements (0.7) (12.0) (0.7) (12.1)        
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 $ 0.0 $ 0.5 $ 0.0 $ (1.7)