Annual report pursuant to Section 13 and 15(d)

Stock Plans and Management Compensation (Details 3)

v3.24.0.1
Stock Plans and Management Compensation (Details 3) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Share-Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Percentage of Premium Paid Out in Deferred Company Common Stock 20.00%    
Performance Shares [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-Based Compensation Expense $ 2.1 $ 3.6 $ 13.5
Share-Based Compensation Expense, Tax Benefit 0.5 0.9 3.3
Fair Value of Shares Vested During the Period $ 16.2 $ 14.6 $ 18.6
Share-Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Outstanding at January 1 191,000    
Awarded Grants in Period 206,000    
Forfeited (13,000)    
Vested (167,000)    
Outstanding at December 31 217,000 191,000  
Weighted Average Grant Date Fair Value $ 90.09 $ 90.97  
Awarded - Weighted Average Grant Date Fair Value 78.49    
Forfeited - Weighted Average Grant Date Fair Value 87.15    
Vested - Weighted Average Grant Date Fair Value $ 77.02    
Unrecognized Compensation Cost $ 1.3    
Unrecognized Compensation Cost, Period for Recognition 1 year 6 months    
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term 2 years 10 months 24 days 2 years 10 months 24 days 2 years 10 months 24 days
Non-Vested Stock Awards [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-Based Compensation Expense $ 20.4 $ 18.2 $ 16.3
Share-Based Compensation Expense, Tax Benefit 5.0 4.5 4.0
Fair Value of Shares Vested During the Period $ 24.5 $ 16.7 $ 11.3
Share-Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Outstanding at January 1 601,000    
Awarded Grants in Period 278,000    
Forfeited (49,000)    
Vested (253,000)    
Outstanding at December 31 577,000 601,000  
Weighted Average Grant Date Fair Value $ 90.72 $ 82.14  
Awarded - Weighted Average Grant Date Fair Value 88.00 $ 93.62 $ 91.14
Forfeited - Weighted Average Grant Date Fair Value 86.54    
Vested - Weighted Average Grant Date Fair Value $ 68.17    
Unrecognized Compensation Cost $ 14.2    
Age of Grantee   62 years  
Unrecognized Compensation Cost, Period for Recognition 1 year 2 months 12 days    
Awards Vesting Period (in years) 3 years    
Stock Options and SAR's [Member]      
Share-Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Period for Stock Options and SARs to be Exercisable (in years) 10 years    
Awards Vesting Period (in years) 4 years    
Outstanding on December 31 1 month 6 days    
Exercisable and Vested on December 31 1 month 6 days    
Vested and Expected to Vest on December 31 1 month 6 days    
Stock Options and SAR's [Member] | $23.79 [Member]      
Share-Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Outstanding Options, Weighted Average Remaining Years of Contractual Life (in years) 1 year 1 month 6 days    
Stock Options and SAR's [Member] | Greater Than $14.68 [Member]      
Share-Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Outstanding Options, Weighted Average Remaining Years of Contractual Life (in years) 1 month 6 days    
Stock Options and SAR's [Member] | $5.87 to $14.68 [Member]      
Share-Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Outstanding Options, Weighted Average Remaining Years of Contractual Life (in years) 8 months 12 days    
Stock Options and SAR's [Member] | $5.86 [Member]      
Share-Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Outstanding Options, Weighted Average Remaining Years of Contractual Life (in years) 0 years    
Share-based Payment Arrangement, Tranche Two [Member] | Performance Shares [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Weighted Average Price at Grant Date (in dollars per share) $ 83.97 $ 91.62 $ 87.48
Share-Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Awarded Grants in Period 36,170 24,320 24,560
Share-based Payment Arrangement, Tranche One [Member] | Performance Shares [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Weighted Average Price at Grant Date (in dollars per share) $ 88.47 $ 94.59 $ 91.44
Risk-Free Interest Rate 4.30% 1.70% 0.20%
Dividend Yield 1.80% 1.50% 1.20%
Volatility Factor 49.80% 54.80% 65.60%