Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation (Stock Incentive Plan) (Details)

v3.8.0.1
Share-Based Compensation (Stock Incentive Plan) (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value $ 90.16 $ 63.94
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value $ 2.7  
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options $ 4.6  
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition 1 year 9 months 18 days  
Restricted Stock [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized 2,000,000