Investment Securities - Revenue and General Obligation Bonds by Location (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
States and Political Subdivisions [Member]
Marketable Securities [Line Items]
Amortized cost (available-for-sale securities and held-to-maturity securities)	$ 372,313	$ 397,234
Fair market value (available-for-sale securities and held-to-maturity securities)	372,371	381,007
General Obligation Bonds [Member]
Marketable Securities [Line Items]
Amortized cost (available-for-sale securities and held-to-maturity securities)	324,679	342,938
Fair market value (available-for-sale securities and held-to-maturity securities)	324,643	329,160
General Obligation Bonds [Member] | TEXAS
Marketable Securities [Line Items]
Amortized cost (available-for-sale securities and held-to-maturity securities)	146,215	153,209
Fair market value (available-for-sale securities and held-to-maturity securities)	146,589	146,667
General Obligation Bonds [Member] | CALIFORNIA
Marketable Securities [Line Items]
Amortized cost (available-for-sale securities and held-to-maturity securities)	63,316	65,758
Fair market value (available-for-sale securities and held-to-maturity securities)	61,048	60,701
General Obligation Bonds [Member] | WASHINGTON
Marketable Securities [Line Items]
Amortized cost (available-for-sale securities and held-to-maturity securities)	20,212	21,635
Fair market value (available-for-sale securities and held-to-maturity securities)	20,400	21,312
General Obligation Bonds [Member] | Other [Member]
Marketable Securities [Line Items]
Amortized cost (available-for-sale securities and held-to-maturity securities)	94,936	102,336
Fair market value (available-for-sale securities and held-to-maturity securities)	96,606	100,480
Revenue Bonds [Member]
Marketable Securities [Line Items]
Amortized cost (available-for-sale securities and held-to-maturity securities)	47,634	54,296
Fair market value (available-for-sale securities and held-to-maturity securities)	47,728	51,847
Revenue Bonds [Member] | TEXAS
Marketable Securities [Line Items]
Amortized cost (available-for-sale securities and held-to-maturity securities)	8,850	9,216
Fair market value (available-for-sale securities and held-to-maturity securities)	8,899	8,840
Revenue Bonds [Member] | CALIFORNIA
Marketable Securities [Line Items]
Amortized cost (available-for-sale securities and held-to-maturity securities)	3,794	3,788
Fair market value (available-for-sale securities and held-to-maturity securities)	3,735	3,673
Revenue Bonds [Member] | WASHINGTON
Marketable Securities [Line Items]
Amortized cost (available-for-sale securities and held-to-maturity securities)	4,035	4,083
Fair market value (available-for-sale securities and held-to-maturity securities)	3,591	3,490
Revenue Bonds [Member] | Other [Member]
Marketable Securities [Line Items]
Amortized cost (available-for-sale securities and held-to-maturity securities)	30,955	37,209
Fair market value (available-for-sale securities and held-to-maturity securities)	$ 31,503	$ 35,844