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Impairment of Investment Securities - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2019 USD ($) Security | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Number of securities in an unrealized loss positions | Security |  | 36 |  |
Corporate/Mortgage-Backed Securities, Amortized cost |  | $ 896,495,000 | $ 924,054,000 |
Securities available for sale |  | 902,292,000 | 909,247,000 |
Other than-temporary impairment charge | [1] | 0 | 9,164,000 | $ 0
Other investments |  | 15,100,000 | 30,500,000 |
Equity Securities, FV-NI |  | 1,700,000 |  |
Equity Securities, FV-NI, Gain (Loss) |  | 0 |  |
Threshold Percentage of Value Decline in Equity Securities to be considered Other than Temporary Impairment |  |  | 0 | 0
Pooled Trust Preferred Collateralized Debt Obligations [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Other than-temporary impairment charge |  | $ 0 | 0 | $ 0
Obligations of U.S. Government-Sponsored Enterprises [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Total unrealized losses |  | 90.00% |  |
Corporate Securities [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Corporate/Mortgage-Backed Securities, Amortized cost |  | $ 22,919,000 | 20,912,000 |
Securities available for sale |  | $ 23,962,000 | 21,012,000 |
Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage - Backed Securities - Residential [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Total unrealized losses |  | 10.00% |  |
Number of securities in an unrealized loss positions | Security |  | 25 |  |
Corporate/Mortgage-Backed Securities, Amortized cost |  | $ 660,777,000 | 686,906,000 |
Securities available for sale |  | $ 661,947,000 | $ 673,361,000 |
[1] | Represents the increase in cash flows recognized either as principal payments or interest income during the period.

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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 Number of investment positions in available-for-sale investments in a continuous unrealized loss position for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27290-111563 + Details
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- Definition This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 35 -Paragraph 32 -URI http://asc.fasb.org/extlink&oid=118954474&loc=d3e32787-111569 + Details
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- Definition Amount of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714 + 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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- Definition This item represents reductions in the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security because of the sale of impaired securities during the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 8B -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=118939692&loc=SL6284393-111563 + Details
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