Securities - Fair Values and Amortized Costs Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 790,208	$ 737,005
Gross Unrealized Gains	26,563	33,478
Gross Unrealized Losses	(2,888)	(90)
Fair Value	813,883	770,393
Marketable equity securities	3,416	3,300
Total Securities	817,299	773,693
Interest receivable	3,200	3,400
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	63,361	9,980
Gross Unrealized Gains	259	302
Gross Unrealized Losses	(352)	0
Fair Value	63,268	10,282
Obligations of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	78,715	78,755
Gross Unrealized Gains	3,313	4,149
Gross Unrealized Losses	0	0
Fair Value	82,028	82,904
Collateralized mortgage obligations of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	213,394	202,975
Gross Unrealized Gains	5,716	6,410
Gross Unrealized Losses	(1,194)	(89)
Fair Value	217,916	209,296
Residential mortgage-backed securities of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	64,496	66,960
Gross Unrealized Gains	632	818
Gross Unrealized Losses	(1,217)	0
Fair Value	63,911	67,778
Commercial mortgage-backed securities of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	266,292	258,875
Gross Unrealized Gains	11,085	14,806
Gross Unrealized Losses	(124)	0
Fair Value	277,253	273,681
Corporate obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,001	2,021
Gross Unrealized Gains	2	5
Gross Unrealized Losses	(1)	(1)
Fair Value	2,002	2,025
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	101,949	117,439
Gross Unrealized Gains	5,556	6,988
Gross Unrealized Losses	0	0
Fair Value	$ 107,505	$ 124,427