Securities - Amortized Cost and Fair Value by Maturity Date (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Amortized cost
Within one year	$ 653
After one to five years	7,635
After five to ten years	64,764
After ten years	591,567
Total	664,619	$ 717,682
Estimated fair value
Within one year	656
After one to five years	7,834
After five to ten years	69,961
After ten years	619,396
Total	$ 697,847	739,473
Weighted average yield
Within one year	8.24%
After one to five years	5.34%
After five to ten years	3.53%
After ten years	2.63%
Total	2.75%
Mortgage-backed - GSE residential
Amortized cost
Within one year	$ 0
After one to five years	56
After five to ten years	220
After ten years	139,339
Total	139,615	151,037
Estimated fair value
Within one year	0
After one to five years	57
After five to ten years	236
After ten years	144,305
Total	$ 144,598	152,512
Weighted average yield
Within one year	0.00%
After one to five years	4.55%
After five to ten years	3.91%
After ten years	2.04%
Total	2.04%
Collateralized mortgage obligations - GSE residential
Amortized cost
Within one year	$ 0
After one to five years	0
After five to ten years	2,507
After ten years	91,682
Total	94,189	128,876
Estimated fair value
Within one year	0
After one to five years	0
After five to ten years	2,755
After ten years	92,886
Total	$ 95,641	129,212
Weighted average yield
Within one year	0.00%
After one to five years	0.00%
After five to ten years	2.77%
After ten years	1.62%
Total	1.65%
State and political subdivisions
Amortized cost
Within one year	$ 653
After one to five years	7,234
After five to ten years	61,170
After ten years	360,546
Total	429,603	436,448
Estimated fair value
Within one year	656
After one to five years	7,419
After five to ten years	66,034
After ten years	382,205
Total	$ 456,314	456,340
Weighted average yield
Within one year	8.24%
After one to five years	5.33%
After five to ten years	3.58%
After ten years	3.10%
Total	3.22%
Corporate bonds
Amortized cost
Within one year	$ 0
After one to five years	345
After five to ten years	867
After ten years	0
Total	1,212	1,321
Estimated fair value
Within one year	0
After one to five years	358
After five to ten years	936
After ten years	0
Total	$ 1,294	$ 1,409
Weighted average yield
Within one year	0.00%
After one to five years	5.89%
After five to ten years	5.68%
After ten years	0.00%
Total	5.74%