Investment Securities - Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Available-for-sale investments, One year or less	$ 210,937
Available-for-sale investments, After 1 through 5 years	190,635
Available-for-sale investments, After 5 through 10 years	204,097
Available-for-sale investments, After ten years	612,926
Available-for-sale investments, Fair Value	$ 1,218,595	$ 1,218,985
Available-for-sale, Weighted average yield, One year or less (in hundredths)	1.64%
Available-for-sale , Weighted average yield,After 1 through 5 years (in hundredths)	2.57%
Available-for-sale, Weighted average yield,After 5 through 10 years (in hundredths)	2.03%
Available-for-sale , Weighted average yield,After ten years (in hundredths)	1.70%
Available-for-sale , Weighted average yield,Total (in hundredths)	1.88%
Available-for-sale, Full Tax-equivalent yield, One year or less (in hundredths)	1.64%
Available-for-sale, Full Tax-equivalent yield,After 1 through 5 years (in hundredths)	2.58%
Available-for-sale, Full Tax-equivalent yield, After 5 through 10 years (in hundredths)	2.06%
Available-for-sale, Full Tax-equivalent yield,After ten years (in hundredths)	1.72%
Available-for-sale, Full Tax-equivalent yield,Total (in hundredths)	1.90%
Held-to-maturity, Maturity [Abstract]
Held-to-maturity, One Year or less	$ 0
Held-to-maturity, After1 through 5 years	0
Held-to-maturity, After 5 through 10 years	0
Held-to-maturity, After ten years	2,259
Held-to-maturity	$ 2,259	2,954
Held To Maturity Weighted average yield, One year or less	0.00%
Held To Maturity Weighted average yield, After 1 through 5 years	0.00%
Held To Maturity Weighted average yield After 5 through 10 years	0.00%
Held To Maturity Weighted average yield After ten years	0.00%
Held To Maturity Weighted average yield ,Total	0.00%
Held To Maturity, Full tax-equivalent yield , One year or less	0.00%
Held To Maturity, Full tax-equivalent yield , After 1 through 5 years	0.00%
Held To Maturity, Full tax-equivalent yield , After 5 through 10 years	0.00%
Held To Maturity, Full tax-equivalent yield , After ten years	0.00%
Held To Maturity, Full tax-equivalent yield , Total	0.00%
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Available-for-sale investments, One year or less	$ 170,295
Available-for-sale investments, After 1 through 5 years	39,997
Available-for-sale investments, After 5 through 10 years	1,637
Available-for-sale investments, After ten years	0
Available-for-sale investments, Fair Value	211,929	220,527
Obligations of States and Political Subdivisions
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Available-for-sale investments, One year or less	20,023
Available-for-sale investments, After 1 through 5 years	82,929
Available-for-sale investments, After 5 through 10 years	162,387
Available-for-sale investments, After ten years	1,134
Available-for-sale investments, Fair Value	266,473	287,698
Mortgage-backed Securities: GSE Residential
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Available-for-sale investments, One year or less	1,690
Available-for-sale investments, After 1 through 5 years	19,588
Available-for-sale investments, After 5 through 10 years	39,452
Available-for-sale investments, After ten years	611,792
Available-for-sale investments, Fair Value	672,522	627,880
Other Securities
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Available-for-sale investments, One year or less	18,929
Available-for-sale investments, After 1 through 5 years	48,121
Available-for-sale investments, After 5 through 10 years	621
Available-for-sale investments, After ten years	0
Available-for-sale investments, Fair Value	67,671	82,880
Other Investments
Held-to-maturity, Maturity [Abstract]
Held-to-maturity, One Year or less	0
Held-to-maturity, After1 through 5 years	0
Held-to-maturity, After 5 through 10 years	0
Held-to-maturity, After ten years	2,259
Held-to-maturity	$ 2,259	$ 2,954