Investment Securities - Additional Information (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2020 USD ($) Security	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Securities, Available-for-sale [Line Items]
Number of securities in an unrealized loss positions \| Security	2
Corporate/Mortgage-Backed Securities, Amortized cost	$ 805,515	$ 896,495
Securities available for sale	831,223	902,292
Other than-temporary impairment charge		0	$ 9,164
Other investments	10,600	15,100
Equity Securities, FV-NI	1,700
Gross Unrealized Gains (Losses)	0	3,109
Amortized Cost	805,515	896,495
Held-to-maturity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Pledged Financial Instruments, Not Separately Reported, Other Debt Securities Available-for-sale or Held-for-investment	228,100	306,800
Available-for-sale Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Pledged Financial Instruments, Not Separately Reported, Other Debt Securities Available-for-sale or Held-for-investment	$ 792,100	584,800
Obligations of U.S. Government-Sponsored Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Total unrealized losses	100.00%
Corporate Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Corporate/Mortgage-Backed Securities, Amortized cost	$ 22,941	22,919
Securities available for sale	24,385	23,962
Gross Unrealized Gains (Losses)	0	0
Amortized Cost	22,941	22,919
Sales [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Gross Realized Losses	0	0	4,719
Available-for-sale Securities, Gross Realized Losses	0	7	0
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments	0	(7)	4,719
Calls And Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Gains	70	29	3,383
Available-for-sale Securities, Gross Realized Losses	0	0	0
Gain Losses Maturities And Impairment	$ 70	$ 29	$ 3,383

Gain losses maturities and impairment.

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This item represents the gross gain on maturities of available for sale securities.

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No definition available.

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Percentage Of Total Unrealized Losses

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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No definition available.

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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.

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This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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No definition available.

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This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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No definition available.

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Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale securities.

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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.

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No definition available.

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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.

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-SubTopic 10
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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).

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The carrying amount as of the date of the latest financial statement presented of other securities classified as available for sale or held for investment which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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