Annual report pursuant to Section 13 and 15(d)

Stock Plans and Management Compensation (Details 3)

v3.10.0.1
Stock Plans and Management Compensation (Details 3) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Share-Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Excess Tax Benefit from Share-Based Compensation, Financing Activities $ 3.2 $ 8.0 $ 13.4
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]      
Expected Life of Award 2 years 10 months 24 days 2 years 10 months 24 days 2 years 10 months 24 days
Share-Based Compensation Expense $ 5.9 $ 6.7 $ 6.1
Share-Based Compensation Expense, Tax Benefit 1.5 2.6 2.3
Fair Value of Shares Vested During the Period $ 7.8 $ 5.5 $ 9.1
Share-Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Outstanding at January 1 102,000    
Awarded Grants in Period 176,000    
Forfeited (20,000)    
Vested (167,000)    
Outstanding at December 31 91,000 102,000  
Weighted Average Grant Date Fair Value $ 61.32 $ 50.69  
Awarded - Weighted Average Grant Date Fair Value 59.11    
Forfeited - Weighted Average Grant Date Fair Value 59.07    
Vested - Weighted Average Grant Date Fair Value $ 52.79    
Unrecognized Compensation Cost $ 2.8    
Unrecognized Compensation Cost, Period for Recognition 1 year 6 months    
Share-based Compensation Award, 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) $ 57.19 $ 58.77 $ 37.76
Share-Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Awarded Grants in Period 24,490 26,300 37,430
Share-based Compensation Award, 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) $ 61.59 $ 64.82 $ 38.54
Risk-Free Interest Rate 2.40% 1.50% 0.80%
Dividend Yield 1.30% 1.10% 1.00%
Volatility Factor 38.90% 38.30% 40.80%