XML 81 R64.htm IDEA: XBRL DOCUMENT v3.19.1
Fair Value Stock Options at Grant Date using Weighted-Average Assumption (Detail)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Weighted Average Fair Values [Line Items]      
Historical volatility 34.00% 39.00% 39.00%
Expected term (years) 6 years 6 years 6 years
Risk-free interest rate 2.72% 1.97% 1.37%
Expected dividend yield 1.22% 0.98% 1.10%