Annual report pursuant to Section 13 and 15(d)

Stock-based Expense and Employee Benefits - Awards Granted Assumptions (Detail)

v3.10.0.1
Stock-based Expense and Employee Benefits - Awards Granted Assumptions (Detail) - Market Based Restricted Stock
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Risk-free interest rate 2.50% 1.80% 1.10%
Expected volatility 31.20% 31.60% 41.50%