XML 101 R88.htm IDEA: XBRL DOCUMENT v3.10.0.1
Stock-Based Compensation - Schedule of Assumptions Used in Determining the Estimated the Fair Value of Stock Options (Details) - $ / shares
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Assumptions used in determining the estimated fair value of stock options      
Risk-free interest rate (as a percent) 2.53% 2.41% 1.62%
Expected option life 5 years 11 months 12 days 5 years 11 months 12 days 5 years 11 months 12 days
Dividend yield (as a percent) 0.70% 0.90% 1.00%
Volatility (as a percent) 35.64% 34.74% 38.41%
Weighted-average fair value per option granted $ 24.36 $ 16.93 $ 14.65