XML 71 R57.htm IDEA: XBRL DOCUMENT v3.10.0.1
Stock Option Plan - Stock Options Issued (Detail)
 12 Months Ended
Dec. 31, 2018
USD ($)
$ / shares
shares
Dec. 31, 2017
USD ($)
$ / shares
shares
Dec. 31, 2016
USD ($)
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 1,904,000    
Vested (in shares) 1,174,500    
Exercised (in shares) 566,081    
Forfeited (in shares) 223,750    
Exercisable at December 31 (in shares) 600,919 430,945 375,255
Remaining unexercised (in shares) 1,114,169    
Exercise price (in usd per share) | $ / shares $ 42.98 $ 46.97 $ 45.59
Total value at grant date | $ $ 13,060,000    
Estimated forfeitures | $ 1,843,000    
Expensed in previous years | $ 4,648,000    
Allocated share based compensation | $ 1,558,000 $ 1,448,000 $ 1,348,000
Future expense | $ 2,215,000    
Directors      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Allocated share based compensation | $ $ 108,800 130,700 150,100
Directors | 4/24/2009      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 32,500    
Vested (in shares) 32,500    
Exercised (in shares) 30,000    
Forfeited (in shares) 0    
Exercisable at December 31 (in shares) 2,500    
Remaining unexercised (in shares) 2,500    
Exercise price (in usd per share) | $ / shares $ 32.68    
Volatility 0.344    
Expected life (years) 6 years    
Assumed yield 4.54%    
Risk-free rate 2.19%    
Total value at grant date | $ $ 223,000    
Expensed in previous years | $ 223,000    
Allocated share based compensation | $ 0 0 0
Future expense | $ $ 0    
Directors | 5/7/2010      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 32,500    
Vested (in shares) 32,500    
Exercised (in shares) 27,500    
Forfeited (in shares) 2,500    
Exercisable at December 31 (in shares) 2,500    
Remaining unexercised (in shares) 2,500    
Exercise price (in usd per share) | $ / shares $ 38.76    
Volatility 0.369    
Expected life (years) 5 years    
Assumed yield 4.23%    
Risk-free rate 2.17%    
Total value at grant date | $ $ 288,000    
Expensed in previous years | $ 288,000    
Allocated share based compensation | $ 0 0 0
Future expense | $ $ 0    
Directors | 5/13/2011      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 32,500    
Vested (in shares) 32,500    
Exercised (in shares) 25,000    
Forfeited (in shares) 2,500    
Exercisable at December 31 (in shares) 5,000    
Remaining unexercised (in shares) 5,000    
Exercise price (in usd per share) | $ / shares $ 41.82    
Volatility 0.358    
Expected life (years) 5 years    
Assumed yield 4.16%    
Risk-free rate 1.86%    
Total value at grant date | $ $ 298,000    
Expensed in previous years | $ 298,000    
Allocated share based compensation | $ 0 0 0
Future expense | $ $ 0    
Directors | 5/4/2012      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 35,000    
Vested (in shares) 35,000    
Exercised (in shares) 25,000    
Forfeited (in shares) 0    
Exercisable at December 31 (in shares) 10,000    
Remaining unexercised (in shares) 10,000    
Exercise price (in usd per share) | $ / shares $ 39.29    
Volatility 0.348    
Expected life (years) 5 years    
Assumed yield 4.61%    
Risk-free rate 0.78%    
Total value at grant date | $ $ 257,000    
Expensed in previous years | $ 257,000    
Allocated share based compensation | $ 0 0 0
Future expense | $ $ 0    
Directors | 5/10/2013      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 35,000    
Vested (in shares) 35,000    
Exercised (in shares) 22,500    
Forfeited (in shares) 0    
Exercisable at December 31 (in shares) 12,500    
Remaining unexercised (in shares) 12,500    
Exercise price (in usd per share) | $ / shares $ 44.42    
Volatility 0.333    
Expected life (years) 5 years    
Assumed yield 4.53%    
Risk-free rate 0.82%    
Total value at grant date | $ $ 278,000    
Expensed in previous years | $ 278,000    
Allocated share based compensation | $ 0 0 0
Future expense | $ $ 0    
Directors | 5/9/2014      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 30,000    
Vested (in shares) 30,000    
Exercised (in shares) 17,500    
Forfeited (in shares) 0    
Exercisable at December 31 (in shares) 12,500    
Remaining unexercised (in shares) 12,500    
Exercise price (in usd per share) | $ / shares $ 47.03    
Volatility 0.173    
Expected life (years) 5 years    
Assumed yield 4.48%    
Risk-free rate 1.63%    
Total value at grant date | $ $ 110,000    
Expensed in previous years | $ 110,000    
Allocated share based compensation | $ 0 0 0
Future expense | $ $ 0    
Directors | 5/8/2015      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 35,000    
Vested (in shares) 35,000    
Exercised (in shares) 12,500    
Forfeited (in shares) 0    
Exercisable at December 31 (in shares) 22,500    
Remaining unexercised (in shares) 22,500    
Exercise price (in usd per share) | $ / shares $ 51.07    
Volatility 0.166    
Expected life (years) 5 years    
Assumed yield 4.54%    
Risk-free rate 1.50%    
Total value at grant date | $ $ 125,000    
Expensed in previous years | $ 125,000    
Allocated share based compensation | $ 0 0 0
Future expense | $ $ 0    
Directors | 5/6/2016      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 32,500    
Vested (in shares) 32,500    
Exercised (in shares) 7,500    
Forfeited (in shares) 0    
Exercisable at December 31 (in shares) 25,000    
Remaining unexercised (in shares) 25,000    
Exercise price (in usd per share) | $ / shares $ 57.74    
Volatility 0.166    
Expected life (years) 5 years    
Assumed yield 3.75%    
Risk-free rate 1.23%    
Total value at grant date | $ $ 151,000    
Expensed in previous years | $ 0    
Allocated share based compensation | $ 0 0 151,000
Future expense | $ $ 0    
Directors | 5/5/2017      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 27,500    
Vested (in shares) 27,500    
Exercised (in shares) 0    
Forfeited (in shares) 2,500    
Exercisable at December 31 (in shares) 25,000    
Remaining unexercised (in shares) 25,000    
Exercise price (in usd per share) | $ / shares $ 59.41    
Volatility 0.173    
Expected life (years) 5 years    
Assumed yield 3.45%    
Risk-free rate 1.89%    
Total value at grant date | $ $ 166,000    
Expensed in previous years | $ 0    
Allocated share based compensation | $ 0 166,000 0
Future expense | $ $ 0    
Directors | 5/11/2018      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 27,500    
Vested (in shares) 27,500    
Exercised (in shares) 2,500    
Forfeited (in shares) 0    
Exercisable at December 31 (in shares) 25,000    
Remaining unexercised (in shares) 25,000    
Exercise price (in usd per share) | $ / shares $ 49.46    
Volatility 0.192    
Expected life (years) 5 years    
Assumed yield 3.70%    
Risk-free rate 2.84%    
Total value at grant date | $ $ 169,000    
Expensed in previous years | $ 0    
Allocated share based compensation | $ 169,000 0 0
Future expense | $ $ 0    
Directors | Subtotals      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 320,000    
Vested (in shares) 320,000    
Exercised (in shares) 170,000    
Forfeited (in shares) 7,500    
Exercisable at December 31 (in shares) 142,500    
Remaining unexercised (in shares) 142,500    
Total value at grant date | $ $ 2,065,000    
Expensed in previous years | $ 1,579,000    
Allocated share based compensation | $ 169,000 166,000 151,000
Future expense | $ $ 0    
Officers | 5/13/2011      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 162,500    
Vested (in shares) 118,750    
Exercised (in shares) 103,750    
Forfeited (in shares) 43,750    
Exercisable at December 31 (in shares) 15,000    
Remaining unexercised (in shares) 15,000    
Exercise price (in usd per share) | $ / shares $ 41.82    
Volatility 0.330    
Expected life (years) 8 years    
Assumed yield 4.81%    
Risk-free rate 2.75%    
Total value at grant date | $ $ 1,367,000    
Estimated forfeitures | $ 368,000    
Expensed in previous years | $ 999,000    
Allocated share based compensation | $ 0 0 0
Future expense | $ $ 0    
Weighted average term of remaining future expense 2 years 6 months 11 days    
Officers | 5/4/2012      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 242,500    
Vested (in shares) 107,500    
Exercised (in shares) 92,455    
Forfeited (in shares) 135,000    
Exercisable at December 31 (in shares) 15,045    
Remaining unexercised (in shares) 15,045    
Exercise price (in usd per share) | $ / shares $ 39.29    
Volatility 0.315    
Expected life (years) 8 years    
Assumed yield 5.28%    
Risk-free rate 1.49%    
Total value at grant date | $ $ 1,518,000    
Estimated forfeitures | $ 845,000    
Expensed in previous years | $ 576,000    
Allocated share based compensation | $ 0 0 97,000
Future expense | $ $ 0    
Officers | 5/10/2013      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 202,500    
Vested (in shares) 171,875    
Exercised (in shares) 129,375    
Forfeited (in shares) 30,625    
Exercisable at December 31 (in shares) 42,500    
Remaining unexercised (in shares) 42,500    
Exercise price (in usd per share) | $ / shares $ 44.42    
Volatility 0.304    
Expected life (years) 8 years    
Assumed yield 5.12%    
Risk-free rate 1.49%    
Total value at grant date | $ $ 1,401,000    
Estimated forfeitures | $ 212,000    
Expensed in previous years | $ 762,000    
Allocated share based compensation | $ 0 158,000 269,000
Future expense | $ $ 0    
Officers | 5/9/2014      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 170,000    
Vested (in shares) 168,125    
Exercised (in shares) 46,126    
Forfeited (in shares) 1,875    
Exercisable at December 31 (in shares) 121,999    
Remaining unexercised (in shares) 121,999    
Exercise price (in usd per share) | $ / shares $ 47.03    
Volatility 0.306    
Expected life (years) 7 years    
Assumed yield 4.89%    
Risk-free rate 2.17%    
Total value at grant date | $ $ 1,350,000    
Estimated forfeitures | $ 15,000    
Expensed in previous years | $ 492,000    
Allocated share based compensation | $ 252,000 295,000 296,000
Future expense | $ $ 0    
Officers | 5/8/2015      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 190,000    
Vested (in shares) 140,625    
Exercised (in shares) 20,625    
Forfeited (in shares) 3,125    
Exercisable at December 31 (in shares) 120,000    
Remaining unexercised (in shares) 166,250    
Exercise price (in usd per share) | $ / shares $ 51.07    
Volatility 0.298    
Expected life (years) 7 years    
Assumed yield 4.94%    
Risk-free rate 1.89%    
Total value at grant date | $ $ 1,585,000    
Estimated forfeitures | $ 142,000    
Expensed in previous years | $ 240,000    
Allocated share based compensation | $ 361,000 361,000 360,000
Future expense | $ $ 121,000    
Officers | 5/6/2016      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 194,000    
Vested (in shares) 96,375    
Exercised (in shares) 3,750    
Forfeited (in shares) 1,875    
Exercisable at December 31 (in shares) 92,625    
Remaining unexercised (in shares) 188,375    
Exercise price (in usd per share) | $ / shares $ 57.74    
Volatility 0.185    
Expected life (years) 7 years    
Assumed yield 3.80%    
Risk-free rate 1.55%    
Total value at grant date | $ $ 1,137,000    
Estimated forfeitures | $ 86,000    
Expensed in previous years | $ 0    
Allocated share based compensation | $ 263,000 263,000 175,000
Future expense | $ $ 350,000    
Officers | 5/5/2017      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 205,000    
Vested (in shares) 51,250    
Exercised (in shares) 0    
Forfeited (in shares) 0    
Exercisable at December 31 (in shares) 51,250    
Remaining unexercised (in shares) 205,000    
Exercise price (in usd per share) | $ / shares $ 59.41    
Volatility 0.170    
Expected life (years) 7 years    
Assumed yield 3.50%    
Risk-free rate 2.17%    
Total value at grant date | $ $ 1,324,000    
Estimated forfeitures | $ 92,000    
Expensed in previous years | $ 0    
Allocated share based compensation | $ 308,000 205,000 0
Future expense | $ $ 719,000    
Officers | 5/11/2018      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 217,500    
Vested (in shares) 0    
Exercised (in shares) 0    
Forfeited (in shares) 0    
Exercisable at December 31 (in shares) 0    
Remaining unexercised (in shares) 217,500    
Exercise price (in usd per share) | $ / shares $ 49.46    
Volatility 0.177    
Expected life (years) 7 years    
Assumed yield 3.75%    
Risk-free rate 2.94%    
Total value at grant date | $ $ 1,313,000    
Estimated forfeitures | $ 83,000    
Expensed in previous years | $ 0    
Allocated share based compensation | $ 205,000 0 0
Future expense | $ $ 1,025,000    
Officers | Subtotals      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total grant (in shares) 1,584,000    
Vested (in shares) 854,500    
Exercised (in shares) 396,081    
Forfeited (in shares) 216,250    
Exercisable at December 31 (in shares) 458,419    
Remaining unexercised (in shares) 971,669    
Total value at grant date | $ $ 10,995,000    
Estimated forfeitures | $ 1,843,000    
Expensed in previous years | $ 3,069,000    
Allocated share based compensation | $ 1,389,000 $ 1,282,000 $ 1,197,000
Future expense | $ $ 2,215,000