Investment Securities - Available for Sale and Held for Maturity Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Available-for-sale: [Abstract]
Amortized Cost	$ 1,470,569	$ 1,432,372
Gross Unrealized Gains	2,064	143
Gross Unrealized (Losses)	(254,038)	(213,530)
Fair Value	1,218,595	1,218,985
Held-to-maturity: [Abstract]
Held-to-maturity	2,259	2,954
Gross Unrealized Gains	0	0
Unrealized (Losses)	0	0
Fair Value	2,259	2,954
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies
Available-for-sale: [Abstract]
Amortized Cost	245,648	252,934
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(33,719)	(32,407)
Fair Value	211,929	220,527
Obligations of States and Political Subdivisions
Available-for-sale: [Abstract]
Amortized Cost	341,002	347,409
Gross Unrealized Gains	28	134
Gross Unrealized (Losses)	(74,557)	(59,845)
Fair Value	266,473	287,698
Mortgage-backed Securities: GSE Residential
Available-for-sale: [Abstract]
Amortized Cost	810,113	744,636
Gross Unrealized Gains	2,036	3
Gross Unrealized (Losses)	(139,627)	(116,759)
Fair Value	672,522	627,880
Other Securities
Available-for-sale: [Abstract]
Amortized Cost	73,806	87,393
Gross Unrealized Gains	0	6
Gross Unrealized (Losses)	(6,135)	(4,519)
Fair Value	67,671	82,880
Other Investments
Held-to-maturity: [Abstract]
Held-to-maturity	2,259	2,954
Gross Unrealized Gains	0	0
Unrealized (Losses)	0	0
Fair Value	$ 2,259	$ 2,954

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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