XML 60 R49.htm IDEA: XBRL DOCUMENT v3.10.0.1
Share-Based Compensation - Stock Option Award Vesting and Weighted Average Assumptions (Details) - Stock Options - $ / shares
6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Weighted average assumptions and weighted average fair value of options    
Number of options granted (in shares) 360,118 548,265
Weighted average exercise price (in dollars per share) $ 86.90 $ 54.90
Risk-free interest rate (as a percent) 2.55% 1.78%
Expected volatility (as a percent) 21.80% 21.71%
Expected term (years) 4 years 9 months 18 days 4 years 7 months 6 days
Dividend yield (as a percent) 0.60% 0.73%
Weighted average fair value (in dollars per share) $ 19.23 $ 10.83
Maximum    
Share-based Compensation    
Award vesting period 3 years