| Schedule of other comprehensive income loss | 
 | 
 | 
Before | 
 | 
Tax | 
 | 
Net of | 
 
 | 
 | 
Tax | 
 | 
(Expense) | 
 | 
Tax | 
 
| (Dollars in Thousands) | 
 | 
Amount | 
 | 
Benefit | 
 | 
Amount | 
 
| 2019 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Investment Securities: | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Change in net unrealized gain (loss) on securities available for sale | 
 | 
$ | 
3,790 | 
 | 
$ | 
(950) | 
 | 
$ | 
2,840 | 
 
| Amortization of losses on securities transferred from available for sale to | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| held to maturity | 
43 | 
 | 
 | 
(11) | 
 | 
 | 
32 | 
 
| Total Investment Securities | 
 | 
 | 
3,833 | 
 | 
 | 
(961) | 
 | 
 | 
2,872 | 
 
| Benefit Plans: | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Reclassification adjustment for amortization of prior service cost | 
 | 
 | 
15 | 
 | 
 | 
(4) | 
 | 
 | 
11 | 
 
| Reclassification adjustment for amortization of net loss | 
 | 
 | 
4,623 | 
 | 
 | 
(1,170) | 
 | 
 | 
3,453 | 
 
| Current year actuarial loss | 
 | 
 | 
(7,642) | 
 | 
 | 
1,940 | 
 | 
 | 
(5,702) | 
 
| Total Benefit Plans | 
 | 
 | 
(3,004) | 
 | 
 | 
766 | 
 | 
 | 
(2,238) | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Total Other Comprehensive Income | 
 | 
$ | 
829 | 
 | 
$ | 
(195) | 
 | 
$ | 
634 | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| 2018 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Investment Securities: | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Change in net unrealized gain (loss) on securities available for sale | 
 | 
$ | 
(409) | 
 | 
$ | 
103 | 
 | 
$ | 
(306) | 
 
| Amortization of losses on securities transferred from available for sale to | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| held to maturity | 
55 | 
 | 
 | 
(14) | 
 | 
 | 
41 | 
 
| Total Investment Securities | 
 | 
 | 
(354) | 
 | 
 | 
89 | 
 | 
 | 
(265) | 
 
| Benefit Plans: | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Reclassification adjustment for amortization of prior service cost | 
 | 
 | 
199 | 
 | 
 | 
(50) | 
 | 
 | 
149 | 
 
| Reclassification adjustment for amortization of net loss | 
 | 
 | 
5,299 | 
 | 
 | 
(1,346) | 
 | 
 | 
3,953 | 
 
| Current year actuarial loss | 
 | 
 | 
(815) | 
 | 
 | 
207 | 
 | 
 | 
(608) | 
 
| Total Benefit Plans | 
 | 
 | 
4,683 | 
 | 
 | 
(1,189) | 
 | 
 | 
3,494 | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Total Other Comprehensive Income | 
 | 
$ | 
4,329 | 
 | 
$ | 
(1,100) | 
 | 
$ | 
3,229 | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| 2017 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Investment Securities: | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Change in net unrealized gain (loss) on securities available for sale | 
 | 
$ | 
(1,459) | 
 | 
$ | 
564 | 
 | 
$ | 
(895) | 
 
| Amortization of losses on securities transferred from available for sale to | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| held to maturity | 
73 | 
 | 
 | 
(29) | 
 | 
 | 
44 | 
 
| Total Investment Securities | 
 | 
 | 
(1,386) | 
 | 
 | 
535 | 
 | 
 | 
(851) | 
 
| Benefit Plans: | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Reclassification adjustment for amortization of prior service cost | 
 | 
 | 
223 | 
 | 
 | 
(86) | 
 | 
 | 
137 | 
 
| Reclassification adjustment for amortization of net loss | 
 | 
 | 
4,409 | 
 | 
 | 
(1,622) | 
 | 
 | 
2,787 | 
 
| Current year actuarial loss | 
 | 
 | 
(3,470) | 
 | 
 | 
1,159 | 
 | 
 | 
(2,311) | 
 
| Total Benefit Plans | 
 | 
 | 
1,162 | 
 | 
 | 
(549) | 
 | 
 | 
613 | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Total Other Comprehensive Loss | 
 | 
$ | 
(224) | 
 | 
$ | 
(14) | 
 | 
$ | 
(238) | 
 
  
 | 
| Activity in accumulated other comprehensive loss, net of tax | 
| Accumulated other comprehensive loss was comprised of the following components: | 
 | 
 | 
 | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
Accumulated | 
 
 | 
 | 
Securities | 
 | 
 | 
 | 
 | 
Other | 
 
 | 
 | 
Available | 
 | 
Retirement | 
 | 
Comprehensive | 
 
|  (Dollars in Thousands) | 
 | 
for Sale | 
 | 
Plans | 
 | 
Loss | 
 
| Balance as of January 1, 2019 | 
 | 
$ | 
(2,008) | 
 | 
$ | 
(26,807) | 
 | 
$ | 
(28,815) | 
 
| Other comprehensive income (loss) during the period | 
 | 
 | 
2,872 | 
 | 
 | 
(2,238) | 
 | 
 | 
634 | 
 
| Balance as of December 31, 2019 | 
 | 
$ | 
864 | 
 | 
$ | 
(29,045) | 
 | 
$ | 
(28,181) | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Balance as of January 1, 2018 | 
 | 
$ | 
(1,743) | 
 | 
$ | 
(30,301) | 
 | 
$ | 
(32,044) | 
 
| Other comprehensive (loss) income during the period | 
 | 
 | 
(265) | 
 | 
 | 
3,494 | 
 | 
 | 
3,229 | 
 
| Balance as of December 31, 2018 | 
 | 
$ | 
(2,008) | 
 | 
$ | 
(26,807) | 
 | 
$ | 
(28,815) | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Balance as of January 1, 2017 | 
 | 
$ | 
(583) | 
 | 
$ | 
(25,642) | 
 | 
$ | 
(26,225) | 
 
| Other comprehensive (loss) income during the period | 
 | 
 | 
(851) | 
 | 
 | 
613 | 
 | 
 | 
(238) | 
 
| Adoption of ASU No. 2018-02 | 
 | 
 | 
(309) | 
 | 
 | 
(5,272) | 
 | 
 | 
(5,581) | 
 
| Balance as of December 31, 2017 | 
 | 
$ | 
(1,743) | 
 | 
$ | 
(30,301) | 
 | 
$ | 
(32,044) | 
 
  
 |