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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, 2022 | Dec. 31, 2021
--- | --- | ---
Investment Securities [Line Items] |  |
Amortized Cost | $ 926,875 | $ 1,045,579
Gross Unrealized Gains | 250 | 9,515
Gross Unrealized Losses | (139,710) | (13,714)
Debt Securities, Available-for-Sale | 787,415 | 1,041,380
US Government Agencies Residential Mortgage-backed Securities [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 4,456 | 5,242
Gross Unrealized Gains | 65 | 420
Gross Unrealized Losses | (232) | 0
Debt Securities, Available-for-Sale | 4,289 | 5,662
US Government Agency Debt Securities Commercial [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 334,730 | 365,024
Gross Unrealized Gains | 0 | 1,725
Gross Unrealized Losses | (51,477) | (4,459)
Debt Securities, Available-for-Sale | 283,253 | 362,290
Residential Mortgage Backed Securities [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 545,165 | 632,687
Gross Unrealized Gains | 24 | 6,308
Gross Unrealized Losses | (83,676) | (9,021)
Debt Securities, Available-for-Sale | 461,513 | 629,974
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 | (127) | (19)
Debt Securities, Available-for-Sale | 873 | 981
Obligations of States and Political Subdivisions [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 9,494 | 9,538
Gross Unrealized Gains | 0 | 89
Gross Unrealized Losses | (1,322) | (103)
Debt Securities, Available-for-Sale | 8,172 | 9,524
Corporate Debt Securities [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 32,030 | 32,088
Gross Unrealized Gains | 161 | 973
Gross Unrealized Losses | (2,876) | (112)
Debt Securities, Available-for-Sale | $ 29,315 | $ 32,949

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- Definition 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563 + Details
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- Definition 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563 + Details
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