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Investment Securities - Additional Information (Detail) | 9 Months Ended |
--- | --- | ---
Sep. 30, 2021 USD ($) | Sep. 30, 2020 USD ($) | Dec. 31, 2020 USD ($)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments | $ 0 | $ 0 |
Gain Losses Maturities And Impairment | 16,000 | 47,000 |
Available-for-sale Securities, Gross Realized Gains | 0 | 0 |
Gross Losses | 0 | 0 |
Gross Gains | 16,000 | 47,000 |
Debt Securities, Held-to-maturity, Restricted | 334,500,000 |  | $ 228,100,000
Proceeds from Sale of Available-for-sale Securities | 0 | 0 |
Debt Securities, Available-for-sale, Restricted | $ 802,200,000 |  | 792,100,000
Investment Securities in Unrealized Loss Position, Qualitative Disclosure, Number of Positions, Total | 52 |  |
Amortized Cost | $ 1,117,384,000 |  | 805,515,000
Available-for-sale Securities | 1,124,956,000 |  | 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 | $ 11,000,000 |  | 10,600,000
US Government-sponsored Enterprises Debt Securities [Member] |  |  |
Percent of Unrealized Losses | 98.00% |  |
Available-for-sale Securities | $ 991,000 |  | $ 100,998,000
Corporate Debt Securities [Member] |  |  |
Investment Securities in Unrealized Loss Position, Qualitative Disclosure, Number of Positions, Total | 1 |  | 0
Amortized Cost | $ 28,100,000 |  | $ 22,900,000
Available-for-sale Securities | 29,240,000 |  | $ 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 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 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 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 954 -SubTopic 210 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=120413173&loc=SL6242262-115580 Reference 2: 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 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 954 -SubTopic 210 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=120413209&loc=SL6242269-115581 + 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=123599499&loc=d3e63345-112809 + Details
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- Definition Includes other investments and securities that are not at fair value as of the balance sheet date and those that are not accounted for under the equity method. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(5)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(12)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(1)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 + Details
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- Definition The amount of other than temporary impairment (OTTI) losses on equity securities, OTTI related to credit losses on debt securities, and OTTI losses on debt securities when the entity intends to sell the securities or it is more likely than not that the entity will be required to sell the securities before recovery of its amortized cost basis. Additionally, this item includes OTTI losses recognized during the period on investments accounted for under the cost method of accounting. + References No definition available. + Details
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