Fair Values of Financial Instruments - Summary of Carrying or Reported Values and Corresponding Fair Values for Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities—held to maturity	$ 621,343	$ 616,772
Fixed maturity securities—available-for-sale	441,146	478,730
Equity securities	27,903	18,651
Short-term investments	56,548	14,231
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities—held to maturity	599,421	613,878
Fixed maturity securities—available-for-sale	441,146	478,730
Equity securities	27,903	18,651
Short-term investments	56,548	14,231
Cash and cash equivalents	43,813	40,344
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities—held to maturity	621,343	616,772
Fixed maturity securities—available-for-sale	441,146	478,730
Equity securities	27,903	18,651
Short-term investments	56,548	14,231
Cash and cash equivalents	$ 43,813	$ 40,344

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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740

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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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-Name Accounting Standards Codification
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Amount of investment in marketable security.

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-Publisher FASB
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-Topic 942
-SubTopic 210
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