XML 128 R91.htm IDEA: XBRL DOCUMENT v3.8.0.1
STOCK BASED COMPENSATION - Assumptions Used in Black-Scholes Option Pricing Model (Detail) - $ / shares
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]      
Stock options granted (shares) 456,424 1,100,492 1,056,490
Weighted average fair value at grant date $ 19.46 $ 20.16 $ 22.90
Expected term (in years) 4 years 9 months 25 days 4 years 9 months 7 days 4 years 9 months 14 days
Expected volatility 22.68% 18.28% 16.71%
Expected dividend yield   0.00% 0.00%
Risk free interest rate 1.90% 1.21% 1.47%