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Investment Securities - Additional Information (Detail) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2021 USD ($) | Mar. 31, 2020 USD ($) | Dec. 31, 2020 USD ($)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments | $ 0 | $ 0 |
Gain Losses Maturities And Impairment | 6,000 | 19,000 |
Available-for-sale Securities, Gross Realized Gains | 0 | 0 |
Gross Losses | 0 | 0 |
Gross Gains | 6,000 | 19,000 |
Debt Securities, Held-to-maturity, Restricted | 305,800,000 |  | $ 228,100,000
Proceeds from Sale of Available-for-sale Securities | 0 | 0 |
Debt Securities, Available-for-sale, Restricted | $ 621,900,000 |  | 792,100,000
Investment Securities in Unrealized Loss Position, Qualitative Disclosure, Number of Positions, Total | 49 |  |
Amortized Cost | $ 1,033,361,000 |  | 805,515,000
Available-for-sale Securities | 1,043,258,000 |  | 831,223,000
Other than temporary impairment charges recognized | 0 | 0 |
Other Investments and Securities, at Cost | 1,700,000 |  | 1,700,000
Federal Home Loan Bank Stock | $ 11,800,000 |  | 10,600,000
US Government-sponsored Enterprises Debt Securities [Member] |  |  |
Percent of Unrealized Losses | 88.00% |  |
Available-for-sale Securities | $ 975,000 |  | $ 100,998,000
Corporate Debt Securities [Member] |  |  |
Investment Securities in Unrealized Loss Position, Qualitative Disclosure, Number of Positions, Total | 1 |  | 0
Amortized Cost | $ 23,100,000 |  | $ 22,900,000
Available-for-sale Securities | 24,459,000 |  | $ 24,385,000
Equity Securities [Member] |  |  |
Other than temporary impairment charges recognized | $ 0 | $ 0 |

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- Definition Investment Securities in Unrealized Loss Position, Qualitative Disclosure, Number of Positions, Total + 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 restricted 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 -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 50 -Paragraph 1A -Subparagraph (b)(1)(i) -URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729 + Details
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- Definition Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 325 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=75031641&loc=d3e63345-112809 + Details
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