Fair Values of Financial Instruments - Summary of Carrying or Reported Values and Corresponding Fair Values for Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities—held to maturity	$ 621,654	$ 621,343
Fixed maturity securities—available-for-sale	414,279	441,146
Equity securities	43,437	27,903
Short-term investments	45,898	56,548
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities—held to maturity	585,130	599,421
Fixed maturity securities—available-for-sale	414,279	441,146
Equity securities	43,437	27,903
Short-term investments	45,898	56,548
Cash and cash equivalents	61,757	43,813
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities—held to maturity	621,654	621,343
Fixed maturity securities—available-for-sale	414,279	441,146
Equity securities	43,437	27,903
Short-term investments	45,898	56,548
Cash and cash equivalents	$ 61,757	$ 43,813

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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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
-Publisher FASB
-Name Accounting Standards Codification
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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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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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Amount of investment in marketable security.

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