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Investment Securities - Analysis of Amortized Cost and Estimated Fair Values of Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Investment Securities [Line Items]
Amortized Cost	$ 978,690	$ 898,702
Gross Unrealized Gains	11	275
Gross Unrealized Losses	(161,098)	(136,316)
Debt Securities, Available-for-Sale	817,603	762,661
US Government Agencies Residential Mortgage-backed Securities [Member]
Investment Securities [Line Items]
Amortized Cost	3,678	4,127
Gross Unrealized Gains	10	37
Gross Unrealized Losses	(262)	(181)
Debt Securities, Available-for-Sale	3,426	3,983
US Government Agency Debt Securities Commercial [Member]
Investment Securities [Line Items]
Amortized Cost	429,282	324,306
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(64,471)	(52,890)
Debt Securities, Available-for-Sale	364,811	271,416
Residential Mortgage Backed Securities [Member]
Investment Securities [Line Items]
Amortized Cost	501,750	527,777
Gross Unrealized Gains	1	59
Gross Unrealized Losses	(90,493)	(78,847)
Debt Securities, Available-for-Sale	411,258	448,989
US Government-sponsored Enterprises Debt Securities [Member]
Investment Securities [Line Items]
Amortized Cost	1,000	1,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(113)	(118)
Debt Securities, Available-for-Sale	887	882
Obligations of States and Political Subdivisions [Member]
Investment Securities [Line Items]
Amortized Cost	9,228	9,482
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,475)	(1,295)
Debt Securities, Available-for-Sale	7,753	8,187
Corporate Debt Securities [Member]
Investment Securities [Line Items]
Amortized Cost	33,752	32,010
Gross Unrealized Gains	0	179
Gross Unrealized Losses	(4,284)	(2,985)
Debt Securities, Available-for-Sale	$ 29,468	$ 29,204

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- Definition

Investment Securities [Line Items]

+ References

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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

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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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1))
-Publisher FASB
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Amount 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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
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-Publisher FASB
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-Topic 942
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