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Investment Securities - Analysis of Amortized Cost and Estimated Fair Values of Securities Available for Sale (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Investment Securities [Line Items] |  |
Amortized Cost | $ 896,495 | $ 924,054
Gross Unrealized Gains | 8,906 | 2,998
Gross Unrealized Losses | (3,109) | (17,805)
Securities available for sale | 902,292 | 909,247
US States and Political Subdivisions Debt Securities [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 17,738 | 27,592
Gross Unrealized Gains | 171 | 126
Gross Unrealized Losses | 0 | (6)
Securities available for sale | 17,909 | 27,712
Corporate Securities [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 22,919 | 20,912
Gross Unrealized Gains | 1,043 | 321
Gross Unrealized Losses | 0 | (221)
Securities available for sale | 23,962 | 21,012
Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage - Backed Securities - Residential [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 660,777 | 686,906
Gross Unrealized Gains | 4,113 | 1,846
Gross Unrealized Losses | (2,943) | (15,391)
Securities available for sale | 661,947 | 673,361
Obligations of U.S. Government-Sponsored Enterprises [Member] | Other Government - Sponsored Enterprises [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 1,000 | 10,000
Gross Unrealized Gains | 0 | 12
Gross Unrealized Losses | 0 | 0
Securities available for sale | 1,000 | 10,012
Obligations of U.S. Government [Member] | Mortgage - Backed Securities - Commercial [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 186,316 | 169,633
Gross Unrealized Gains | 2,983 | 214
Gross Unrealized Losses | (166) | (2,103)
Securities available for sale | 189,133 | 167,744
Obligations of U.S. Government [Member] | Mortgage - Backed Securities - Residential [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 7,745 | 9,011
Gross Unrealized Gains | 596 | 479
Gross Unrealized Losses | 0 | (84)
Securities available for sale | $ 8,341 | $ 9,406

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- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References No definition available. + Details
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- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References No definition available. + Details
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- Definition Amount of unrealized gain before deducting unrealized loss on investments in debt and equity securities classified as available-for-sale securities. + 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 http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
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- Definition Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale securities. + 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 http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
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