Investment Securities - Fair Value of Investments with Sustained Gross Unrealized Losses (Details) - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available-for-sale, Less than 12 months, Fair Value	$ 982,049,000	$ 680,526,000
Available-for-sale, Less than 12 months, Unrealized Losses	(72,996,000)	(13,708,000)
Available-for-sale, 12 months or longer, Fair Value	319,139,000	186,350,000
Available-for-sale, 12 months or longer, Unrealized losses	(34,538,000)	(4,627,000)
Available-for-sale, Total Fair Value	1,301,188,000	866,876,000
Available-for-sale, Total Unrealized Losses	(107,534,000)	(18,335,000)
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available-for-sale, Less than 12 months, Fair Value	124,219,000	48,316,000
Available-for-sale, Less than 12 months, Unrealized Losses	(5,410,000)	(1,927,000)
Available-for-sale, 12 months or longer, Fair Value	116,577,000	139,846,000
Available-for-sale, 12 months or longer, Unrealized losses	(11,117,000)	(2,936,000)
Available-for-sale, Total Fair Value	240,796,000	188,162,000
Available-for-sale, Total Unrealized Losses	(16,527,000)	(4,863,000)
Obligations of States and Political Subdivisions
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available-for-sale, Less than 12 months, Fair Value	231,248,000	61,535,000
Available-for-sale, Less than 12 months, Unrealized Losses	(29,282,000)	(657,000)
Available-for-sale, 12 months or longer, Fair Value	6,399,000	0
Available-for-sale, 12 months or longer, Unrealized losses	(1,241,000)	0
Available-for-sale, Total Fair Value	237,647,000	61,535,000
Available-for-sale, Total Unrealized Losses	(30,523,000)	(657,000)
Mortgage-backed Securities: GSE Residential
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available-for-sale, Less than 12 months, Fair Value	546,117,000	562,699,000
Available-for-sale, Less than 12 months, Unrealized Losses	(37,044,000)	(11,019,000)
Available-for-sale, 12 months or longer, Fair Value	193,648,000	46,504,000
Available-for-sale, 12 months or longer, Unrealized losses	(22,122,000)	(1,691,000)
Available-for-sale, Total Fair Value	739,765,000	609,203,000
Available-for-sale, Total Unrealized Losses	(59,166,000)	(12,710,000)
Other Securities
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available-for-sale, Less than 12 months, Fair Value	80,465,000	7,976,000
Available-for-sale, Less than 12 months, Unrealized Losses	(1,260,000)	(105,000)
Available-for-sale, 12 months or longer, Fair Value	2,515,000	0
Available-for-sale, 12 months or longer, Unrealized losses	(58,000)	0
Available-for-sale, Total Fair Value	82,980,000	7,976,000
Available-for-sale, Total Unrealized Losses	$ (1,318,000)	$ (105,000)