Investment Securities - Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Available-for-sale investments, One year or less	$ 208,151
Available-for-sale investments, After 1 through 5 years	390,861
Available-for-sale investments, After 5 through 10 years	864,737
Available-for-sale investments, After ten years	3,201
Available-for-sale investments, Fair Value	$ 1,466,950	$ 1,421,422
Available-for-sale, Weighted average yield, One year or less (in hundredths)	1.47%
Available-for-sale , Weighted average yield,After 1 through 5 years (in hundredths)	2.34%
Available-for-sale, Weighted average yield,After 5 through 10 years (in hundredths)	1.76%
Available-for-sale , Weighted average yield,After ten years (in hundredths)	2.93%
Available-for-sale , Weighted average yield,Total (in hundredths)	1.87%
Available-for-sale, Full Tax-equivalent yield, One year or less (in hundredths)	1.59%
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)	1.94%
Available-for-sale, Full Tax-equivalent yield,After ten years (in hundredths)	3.43%
Available-for-sale, Full Tax-equivalent yield,Total (in hundredths)	2.06%
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	2,998
Held-to-maturity	$ 2,998	7,030
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	$ 155,050
Available-for-sale investments, After 1 through 5 years	82,575
Available-for-sale investments, After 5 through 10 years	10,351
Available-for-sale investments, After ten years	0
Available-for-sale investments, Fair Value	247,976	203,815
Held-to-maturity, Maturity [Abstract]
Held-to-maturity		5,001
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	20,894
Available-for-sale investments, After 1 through 5 years	94,654
Available-for-sale investments, After 5 through 10 years	241,873
Available-for-sale investments, After ten years	1,258
Available-for-sale investments, Fair Value	358,679	395,457
Mortgage-backed Securities: GSE Residential
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Available-for-sale investments, One year or less	9,460
Available-for-sale investments, After 1 through 5 years	139,057
Available-for-sale investments, After 5 through 10 years	611,067
Available-for-sale investments, After ten years	1,943
Available-for-sale investments, Fair Value	761,527	791,038
Other Securities
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Available-for-sale investments, One year or less	22,747
Available-for-sale investments, After 1 through 5 years	74,575
Available-for-sale investments, After 5 through 10 years	1,446
Available-for-sale investments, After ten years	0
Available-for-sale investments, Fair Value	98,768	31,112
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	2,998
Held-to-maturity	$ 2,998	$ 2,029