Annual report pursuant to Section 13 and 15(d)

Stock Based Compensation - Additional Information (Detail)

v3.22.0.1
Stock Based Compensation - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Shares authorized for issuance under the Plan 150,000       841,500
Shares outstanding under the Plans 24,750 24,750 24,750 34,500  
Percentage of annual fees in the form of non-vested shares 80.00%        
Share based compensation, expiration date May 21, 2020        
Shares outstanding under the Plans, non-vested shares 149,487 154,770 147,723 145,004  
Common stock authorized for issuance 131,810        
Intrinsic value of stock options exercised     $ 100,000    
Proceeds from stock options exercised     $ 500,000    
Fair market value of the non-vested stock on the date of grant $ 114.61 $ 71.70 $ 67.33    
Shares granted under performance plan 55,433 60,288 57,849    
Equity Program [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Weighted average remaining contractual life of all exercisable options (in years) 2 years 4 months 24 days        
Directors [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Shares of non-vested stock issued 4,416        
Shares defered in period 3,054        
Deferred compensation expense $ 117,000 $ 0 $ 0    
Deferred Compensation Plan For Directors [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Shares outstanding under Deferred Compensation Plan 35,135        
Stock Options [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of shares available for grant for future issuance 170,111        
Shares outstanding under the Plans 0        
Common shares options outstanding 24,750        
Non-Vested Shares [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Shares outstanding under the Plans, non-vested shares 15,137        
Compensation expense-vested portion of non-vested stock grants $ 6,600,000 4,600,000 4,200,000    
Non-vested stock, aggregate fair value 4,100,000 $ 2,900,000 $ 3,200,000    
Total unrecognized compensation $ 11,200,000        
Cost recognition, weighted-average period 4 years        
Non-Vested Shares [Member] | Employees And Directors [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Shares of non-vested stock issued 55,433        
Aggregate fair value $ 6,400,000        
Performance Shares [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Stock option plan, share based compensation, vesting period (in years) 3 years        
Compensation expense-vested portion of non-vested stock grants $ 6,600,000        
Total unrecognized compensation $ 5,500,000        
Cost recognition, weighted-average period 2 years 3 months 18 days        
Shares granted under performance plan 53,680 53,541 22,331    
Compensation expense-Performance awards $ 2,300,000        
Maximum [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Stock option plan, share based compensation, vesting period (in years) 8 years        
Maximum [Member] | Non-Vested Shares [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Fair market value of the non-vested stock on the date of grant $ 144.63        
Maximum [Member] | Performance Shares [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Shares granted under performance plan 53,034 70,272 59,634    
Minimum [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Stock option plan, share based compensation, vesting period (in years) 2 years        
Minimum [Member] | Non-Vested Shares [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Stock option plan, share based compensation, vesting period (in years) 1 year        
Fair market value of the non-vested stock on the date of grant $ 84.06