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Investments - Investments - Changes in Allowance for Credit Losses by Major Security Type of Investments Classified as Held-to-Maturity (Detail) $ in Thousands | 12 Months Ended
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Dec. 31, 2023 USD ($)
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Balance | $ 239
Provision for credit loss expense (benefit) | (57)
Balance | 182
Amortized cost | 483,757
AAA/AA/A Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 451,168
Baa/BBB Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 32,589
States and Political Subdivisions [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Balance | 40
Provision for credit loss expense (benefit) | (2)
Balance | 38
Amortized cost | 416,916
States and Political Subdivisions [Member] | AAA/AA/A Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 413,966
States and Political Subdivisions [Member] | Baa/BBB Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 2,950
Corporate Bonds [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Balance | 196
Provision for credit loss expense (benefit) | (54)
Balance | 142
Amortized cost | 52,321
Corporate Bonds [Member] | AAA/AA/A Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 22,696
Corporate Bonds [Member] | Baa/BBB Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 29,625
U.S. Agency-Based Mortgage-Backed Securities [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 3,297
U.S. Agency-Based Mortgage-Backed Securities [Member] | AAA/AA/A Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 3,297
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 11,186
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member] | AAA/AA/A Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 11,186
Asset-Backed Securities [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Balance | 3
Provision for credit loss expense (benefit) | (1)
Balance | 2
Amortized cost | 37
Asset-Backed Securities [Member] | AAA/AA/A Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 23
Asset-Backed Securities [Member] | Baa/BBB Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | $ 14

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- Definition Amount of allowance for credit loss for debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (aaa) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-5 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479344/326-20-45-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-13 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-13 + Details
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- Definition Amount of expense (reversal of expense) for expected credit loss on investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-13 + Details
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- Definition 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. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-5 + Details
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- Definition Amount of investment in debt security measured at amortized cost (held-to-maturity) originated in current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
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