Securities - Fair Values and Amortized Costs Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 815,280	$ 737,005
Gross Unrealized Gains	25,494	33,478
Gross Unrealized Losses	(1,495)	(90)
Fair Value	839,279	770,393
Marketable equity securities	1,096	3,300
Total Securities	840,375	773,693
Interest receivable	3,200	3,100
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	74,253	9,980
Gross Unrealized Gains	551	302
Gross Unrealized Losses	0	0
Fair Value	74,804	10,282
Obligations of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	78,674	78,755
Gross Unrealized Gains	2,950	4,149
Gross Unrealized Losses	0	0
Fair Value	81,624	82,904
Collateralized mortgage obligations of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	197,458	202,975
Gross Unrealized Gains	4,762	6,410
Gross Unrealized Losses	(870)	(89)
Fair Value	201,350	209,296
Residential mortgage-backed securities of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	63,896	66,960
Gross Unrealized Gains	548	818
Gross Unrealized Losses	(585)	0
Fair Value	63,859	67,778
Commercial mortgage-backed securities of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	314,228	258,875
Gross Unrealized Gains	11,114	14,806
Gross Unrealized Losses	(39)	0
Fair Value	325,303	273,681
Corporate obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	500	2,021
Gross Unrealized Gains	0	5
Gross Unrealized Losses	(1)	(1)
Fair Value	499	2,025
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	86,271	117,439
Gross Unrealized Gains	5,569	6,988
Gross Unrealized Losses	0	0
Fair Value	$ 91,840	$ 124,427