Securities - Amortized Cost and Estimated Fair Value of Securities - Securities Held-to-maturity (Details) - USD ($)	Mar. 31, 2024	Dec. 31, 2023
Securities held-to-maturity:
Total	$ 636,261,000	$ 650,577,000
Gross Unrecognized Gains	84,000	285,000
Gross Unrecognized (Losses)	(93,487,000)	(86,735,000)
Estimated Fair Value	542,858,000	564,127,000
Allowance for credit loss current period	(12,000)	(12,000)
Agency mortgage-backed securities
Securities held-to-maturity:
Total	604,458,000	618,374,000
Gross Unrecognized Gains	83,000	282,000
Gross Unrecognized (Losses)	(92,415,000)	(86,011,000)
Estimated Fair Value	512,126,000	532,645,000
Municipals - exempt from Federal tax
Securities held-to-maturity:
Total	31,803,000	32,203,000
Gross Unrecognized Gains	1,000	3,000
Gross Unrecognized (Losses)	(1,072,000)	(724,000)
Estimated Fair Value	30,732,000	31,482,000
Allowance for credit loss current period	$ (12,000)	$ (12,000)