| Schedule of financial assets and financial liabilities measured at fair value on a recurring basis | 
 | 
 | 
Level 1 | 
   | 
Level 2 | 
   | 
Level 3 | 
   | 
Total Fair  | 
 
| (Dollars in Thousands) | 
Inputs | 
 | 
Inputs | 
 | 
Inputs | 
 | 
Value | 
 
| March 31, 2019 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| ASSETS: | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Securities Available for Sale: | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
 | 
U.S. Government Treasury | 
$ | 
252,941 | 
 | 
$ | 
- | 
 | 
$ | 
- | 
 | 
$ | 
252,941 | 
 
 | 
U.S. Government Agency | 
 | 
- | 
 | 
 | 
133,593 | 
 | 
 | 
- | 
 | 
 | 
133,593 | 
 
 | 
States and Political Subdivisions | 
 | 
- | 
 | 
 | 
33,856 | 
 | 
 | 
- | 
 | 
 | 
33,856 | 
 
 | 
Mortgage-Backed Securities | 
 | 
- | 
 | 
 | 
779 | 
 | 
 | 
- | 
 | 
 | 
779 | 
 
 | 
Equity Securities  | 
 | 
- | 
 | 
 | 
7,847 | 
 | 
 | 
- | 
 | 
 | 
7,847 | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| December 31, 2018 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| ASSETS: | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Securities Available for Sale: | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
 | 
U.S. Government Treasury | 
$ | 
261,849 | 
 | 
$ | 
- | 
 | 
$ | 
- | 
 | 
$ | 
261,849 | 
 
 | 
U.S. Government Agency | 
 | 
- | 
 | 
 | 
133,206 | 
 | 
 | 
- | 
 | 
 | 
133,206 | 
 
 | 
States and Political Subdivisions | 
 | 
- | 
 | 
 | 
42,365 | 
 | 
 | 
- | 
 | 
 | 
42,365 | 
 
 | 
Mortgage-Backed Securities | 
 | 
- | 
 | 
 | 
943 | 
 | 
 | 
- | 
 | 
 | 
943 | 
 
 | 
Equity Securities  | 
 | 
- | 
 | 
 | 
7,794 | 
 | 
 | 
- | 
 | 
 | 
7,794 | 
 
  
 | 
| Schedule of financial instruments with estimated fair values | 
|    | 
 | 
March 31, 2019 | 
 
 | 
 | 
Carrying | 
 | 
Level 1 | 
 | 
Level 2 | 
 | 
Level 3 | 
 
| (Dollars in Thousands) | 
 | 
Value | 
 | 
Inputs | 
 | 
Inputs | 
 | 
Inputs | 
 
| ASSETS: | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Cash | 
 | 
$ | 
49,501 | 
 | 
$ | 
49,501 | 
 | 
$ | 
- | 
 | 
$ | 
- | 
 
| Short-Term Investments | 
 | 
 | 
304,213 | 
 | 
 | 
304,213 | 
 | 
 | 
- | 
 | 
 | 
- | 
 
| Investment Securities, Available for Sale | 
 | 
 | 
429,016 | 
 | 
 | 
252,941 | 
 | 
 | 
176,075 | 
 | 
 | 
- | 
 
| Investment Securities, Held to Maturity | 
 | 
 | 
226,179 | 
 | 
 | 
34,765 | 
 | 
 | 
190,552 | 
 | 
 | 
- | 
 
| 
Equity Securities(1)
 | 
 | 
 | 
3,588 | 
 | 
 | 
- | 
 | 
 | 
3,588 | 
 | 
 | 
- | 
 
| Loans Held for Sale | 
 | 
 | 
4,557 | 
 | 
 | 
- | 
 | 
 | 
4,557 | 
 | 
 | 
- | 
 
| Loans, Net of Allowance for Loan Losses | 
 | 
 | 
1,782,985 | 
 | 
 | 
- | 
 | 
 | 
- | 
 | 
 | 
1,760,136 | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| LIABILITIES: | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Deposits | 
 | 
$ | 
2,617,294 | 
 | 
$ | 
- | 
 | 
$ | 
2,615,572 | 
 | 
$ | 
- | 
 
| Short-Term Borrowings | 
 | 
 | 
8,983 | 
 | 
 | 
- | 
 | 
 | 
8,983 | 
 | 
 | 
- | 
 
| Subordinated Notes Payable | 
 | 
 | 
52,887 | 
 | 
 | 
- | 
 | 
 | 
41,128 | 
 | 
 | 
- | 
 
| Long-Term Borrowings | 
 | 
 | 
7,661 | 
 | 
 | 
- | 
 | 
 | 
7,715 | 
 | 
 | 
- | 
 
  
|    | 
 | 
December 31, 2018 | 
 
 | 
 | 
Carrying | 
 | 
Level 1 | 
 | 
Level 2 | 
 | 
Level 3 | 
 
| (Dollars in Thousands) | 
 | 
Value | 
 | 
Inputs | 
 | 
Inputs | 
 | 
Inputs | 
 
| ASSETS: | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Cash | 
 | 
$ | 
62,032 | 
 | 
$ | 
62,032 | 
 | 
$ | 
- | 
 | 
$ | 
- | 
 
| Short-Term Investments | 
 | 
 | 
213,968 | 
 | 
 | 
213,968 | 
 | 
 | 
- | 
 | 
 | 
- | 
 
| Investment Securities, Available for Sale | 
 | 
 | 
446,157 | 
 | 
 | 
261,849 | 
 | 
 | 
184,308 | 
 | 
 | 
- | 
 
| Investment Securities, Held to Maturity | 
 | 
 | 
217,320 | 
 | 
 | 
34,611 | 
 | 
 | 
179,802 | 
 | 
 | 
- | 
 
| Loans Held for Sale | 
 | 
 | 
6,869 | 
 | 
 | 
- | 
 | 
 | 
6,869 | 
 | 
 | 
- | 
 
| 
Equity Securities(1)
 | 
 | 
 | 
3,591 | 
 | 
 | 
- | 
 | 
 | 
3,591 | 
 | 
 | 
- | 
 
| Loans, Net of Allowance for Loan Losses | 
 | 
 | 
1,760,015 | 
 | 
 | 
- | 
 | 
 | 
- | 
 | 
 | 
1,730,161 | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| LIABILITIES: | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
| Deposits | 
 | 
$ | 
2,531,856 | 
 | 
$ | 
- | 
 | 
$ | 
2,529,841 | 
 | 
$ | 
- | 
 
| Short-Term Borrowings | 
 | 
 | 
13,541 | 
 | 
 | 
- | 
 | 
 | 
13,541 | 
 | 
 | 
- | 
 
| Subordinated Notes Payable | 
 | 
 | 
52,887 | 
 | 
 | 
- | 
 | 
 | 
42,359 | 
 | 
 | 
- | 
 
| Long-Term Borrowings | 
 | 
 | 
8,568 | 
 | 
 | 
- | 
 | 
 | 
7,879 | 
 | 
 | 
- | 
 
  
 |