Securities - Amortized Cost and Fair Value by Maturity Date (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Amortized cost
Within one year	$ 522
After one to five years	5,849
After five to ten years	76,307
After ten years	594,145
Total	676,823	$ 615,654
Estimated fair value
Within one year	524
After one to five years	5,952
After five to ten years	82,655
After ten years	623,086
Total	$ 712,217	654,588
Weighted average yield
Within one year	3.18%
After one to five years	3.83%
After five to ten years	3.43%
After ten years	2.52%
Total	2.63%
Mortgage-backed - GSE residential
Amortized cost
Within one year	$ 0
After one to five years	40
After five to ten years	181
After ten years	143,866
Total	144,087	104,839
Estimated fair value
Within one year	0
After one to five years	42
After five to ten years	195
After ten years	145,467
Total	$ 145,704	109,116
Weighted average yield
Within one year	0.00%
After one to five years	4.62%
After five to ten years	3.98%
After ten years	1.73%
Total	1.73%
Collateralized mortgage obligations - GSE residential
Amortized cost
Within one year	$ 0
After one to five years	0
After five to ten years	2,454
After ten years	25,981
Total	28,435	52,070
Estimated fair value
Within one year	0
After one to five years	0
After five to ten years	2,643
After ten years	26,387
Total	$ 29,030	53,012
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	1.31%
Total	1.44%
State and political subdivisions
Amortized cost
Within one year	$ 522
After one to five years	5,453
After five to ten years	69,778
After ten years	424,298
Total	500,051	454,486
Estimated fair value
Within one year	524
After one to five years	5,547
After five to ten years	75,899
After ten years	451,232
Total	$ 533,202	488,097
Weighted average yield
Within one year	3.18%
After one to five years	3.80%
After five to ten years	3.39%
After ten years	2.86%
Total	2.95%
Corporate bonds
Amortized cost
Within one year	$ 0
After one to five years	356
After five to ten years	3,894
After ten years	0
Total	4,250	4,259
Estimated fair value
Within one year	0
After one to five years	363
After five to ten years	3,918
After ten years	0
Total	$ 4,281	$ 4,363
Weighted average yield
Within one year	0.00%
After one to five years	4.22%
After five to ten years	4.53%
After ten years	0.00%
Total	4.51%