Securities - Available-for-Sale Securities Held by Company (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,795,423	$ 1,831,791
Gross Unrealized Gains	25	20
Gross Unrealized Losses	209,594	236,844
Fair Value	1,585,854	1,594,967
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	190,220	190,170
Gross Unrealized Gains	0	0
Gross Unrealized Losses	19,406	22,919
Fair Value	170,814	167,251
Obligations of U.S. Government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	670,978	681,192
Gross Unrealized Gains	0	0
Gross Unrealized Losses	71,216	80,025
Fair Value	599,762	601,167
Obligations of U.S. states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	92,915	93,599
Gross Unrealized Gains	10	8
Gross Unrealized Losses	6,241	8,326
Fair Value	86,684	85,281
U.S. Government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	56,224	58,727
Gross Unrealized Gains	15	12
Gross Unrealized Losses	5,348	6,071
Fair Value	50,891	52,668
U.S. Government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	782,586	805,603
Gross Unrealized Gains	0	0
Gross Unrealized Losses	107,276	119,381
Fair Value	675,310	686,222
U.S. corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,500	2,500
Gross Unrealized Gains	0	0
Gross Unrealized Losses	107	122
Fair Value	$ 2,393	$ 2,378

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).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
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Amount, before tax, of unrealized loss 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).

+ References

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Amortized cost excluding accrued interest, before allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

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Amount excluding accrued interest, of 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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-Publisher FASB
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