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Investment Securities - Proceeds from Sale, Gross Gains (Losses) Realized on Sales, Maturities and Other-Than-Temporary Impairment Charges Related to Securities Available for Sale (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Gain (Loss) on Securities [Line Items] |  |  |
Proceeds from sale | $ 948 | $ 15,939 | $ 143,660
Net gains (losses) and impairment | 22 | 8,102 | 5,040
Calls And Maturities [Member] |  |  |
Gain (Loss) on Securities [Line Items] |  |  |
Gross losses | 0 | 0 | (60)
Gross gains | 29 | 3,383 | 5,057
Other-than-temporary impairment | 0 | 0 | 0
Total gain (losses) maturities and impairment | 29 | 3,383 | 4,997
Sales [Member] |  |  |
Gain (Loss) on Securities [Line Items] |  |  |
Gross losses | (7) | 0 | (316)
Available-for-sale Securities, Gross Realized Losses | 0 | 4,719 | 359
Total gain (losses) from sales transactions | $ (7) | $ 4,719 | $ 43

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- Definition This item represents the gross gain on maturities of available for sale securities. + References No definition available. + Details
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- Definition This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References No definition available. + Details
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- Definition This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References No definition available. + Details
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- Definition This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References No definition available. + Details
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- Definition Amount of cash inflow from sale 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26853-111562 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3151-108585 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585 + Details
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