Securities (Schedule of Securities Available-for-Sale) (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,681,122,000	$ 1,172,175,000
Gross Unrealized Gains	32,698,000	46,003,000
Gross Unrealized Losses	(17,595,000)	(326,000)
Allowance for Credit Losses	0	0
Fair Value	1,696,225,000	1,217,852,000
Obligations of State and Political Subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	813,088,000	548,273,000
Gross Unrealized Gains	26,425,000	33,077,000
Gross Unrealized Losses	(6,060,000)	(103,000)
Allowance for Credit Losses	0	0
Fair Value	833,453,000	581,247,000
MBS/CMO
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	728,789,000	535,526,000
Gross Unrealized Gains	6,250,000	12,806,000
Gross Unrealized Losses	(8,407,000)	(25,000)
Allowance for Credit Losses	0	0
Fair Value	726,632,000	548,307,000
US Gov't Sponsored Entities & Agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	139,245,000	88,376,000
Gross Unrealized Gains	23,000	120,000
Gross Unrealized Losses	(3,128,000)	(198,000)
Allowance for Credit Losses	0	0
Fair Value	$ 136,140,000	$ 88,298,000

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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-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).

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Amount excluding accrued interest, of allowance for credit loss 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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-Publisher FASB
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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).

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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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