Comprehensive Income (Tables)
 12 Months Ended
Dec. 31, 2016
Comprehensive Income [Abstract]  
Accumulated Balances of Other Comprehensive Income
The accumulated balances for each classification of other comprehensive income are as follows:
 
 
Unrealized
Gains on
securities
  
Liability
for Pension
Benefits
  
Accumulated
Other
Comprehensive
Income
 
          
Beginning balance at December 31, 2015
 
$
62,478
  
$
(36,855
)
 
$
25,623
 
Net current period change
  
14,761
   
15,728
   
30,489
 
Reclassification adjustments for gains and losses reclassified in income
  
(14,868
)
  
1,151
   
(13,717
)
Ending balance at December 31, 2016
 
$
62,371
  
$
(19,976
)
 
$
42,395
 
Summary of Related Deferred Tax Effects Allocated to Each Component of Other Comprehensive Income
The related deferred tax effects allocated to each component of other comprehensive income in the accompanying consolidated statements of stockholders’ equity and comprehensive income in 2016, 2015 and 2014 are as follows:

  
2016
 
  
Before-Tax
Amount
  
Deferred Tax
(Expense)
Benefit
  
Net-of-Tax
Amount
 
         
Unrealized holding gains on securities arising during the period
 
$
18,357
  
$
(3,596
)
 
$
14,761
 
Less reclassification adjustment for gains and losses realized in income
  
(17,379
)
  
2,511
   
(14,868
)
Net change in unrealized gain
  
978
   
(1,085
)
  
(107
)
Liability for pension benefits:
            
Reclassification adjustment for amortization of net losses from past experience and prior service costs
  
1,888
   
(737
)
  
1,151
 
Net change arising from assumptions and plan changes and experience
  
25,783
   
(10,055
)
  
15,728
 
Net change in liability for pension benefits
  
27,671
   
(10,792
)
  
16,879
 
Net current period change
 
$
28,649
  
$
(11,877
)
 
$
16,772
 
 
 
  
2015
 
  
Before-Tax
Amount
  
Deferred Tax
(Expense)
Benefit
  
Net-of-Tax
Amount
 
          
Unrealized holding gains on securities arising during the period
 
$
(25,765
)
 
$
3,153
  
$
(22,612
)
Less reclassification adjustment for gains and losses realized in income
  
(18,941
)
  
2,564
   
(16,377
)
Net change in unrealized gain
  
(44,706
)
  
5,717
   
(38,989
)
Liability for pension benefits:
            
Reclassification adjustment for amortization of net losses from past experience and prior service costs
  
6,020
   
(2,348
)
  
3,672
 
Net change arising from assumptions and plan changes and experience
  
19,940
   
(7,776
)
  
12,164
 
Net change in liability for pension benefits
  
25,960
   
(10,124
)
  
15,836
 
Net current period change
 
$
(18,746
)
 
$
(4,407
)
 
$
(23,153
)
 
 
2014
 
  
Before-Tax
Amount
  
Deferred Tax
(Expense)
Benefit
  
Net-of-Tax
Amount
 
         
Unrealized holding gains on securities arising during the period
 
$
58,831
  
$
(8,161
)
 
$
50,670
 
Less reclassification adjustment for gains and losses realized in income
  
(18,231
)
  
3,444
   
(14,787
)
Net change in unrealized gain
  
40,600
   
(4,717
)
  
35,883
 
Liability for pension benefits:
            
Reclassification adjustment for amortization of net losses from past experience and prior service costs
  
3,737
   
(1,457
)
  
2,280
 
Net change arising from assumptions and plan changes and experience
  
(35,271
)
  
13,755
   
(21,516
)
Net change in liability for pension benefits
  
(31,534
)
  
12,298
   
(19,236
)
Net current period change
 
$
9,066
  
$
7,581
  
$
16,647