Annual report pursuant to Section 13 and 15(d)

Stock Based Compensation - Stock Option Activity and Related Information (Detail)

v3.10.0.1
Stock Based Compensation - Stock Option Activity and Related Information (Detail) - $ / shares
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]      
Outstanding at beginning of year, Options 94,606 95,706 95,706
Exercised, Options (71,606) (1,100) 0
Outstanding at end of year, Options 23,000 94,606 95,706
Exercisable at end of year, Options 23,000 93,106 92,706
Outstanding at beginning of year, Weighted average exercise price $ 52.24 $ 52.08 $ 52.08
Exercised, Weighted average exercise price 43.68 39.00  
Outstanding at end of year, Weighted average exercise price 78.87 52.24 52.08
Exercisable at end of year, Weighted average exercise price $ 78.87 $ 51.85 $ 51.31