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Investments - Changes in Allowance for Credit Losses by Major Security Type of Investments Classified as Held-to-Maturity (Detail) $ in Thousands | 3 Months Ended
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Mar. 31, 2023 USD ($)
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Balance | $ 239
Provision for credit loss expense (benefit) | 19
Balance | 220
Amortized cost | 480,362
AAA/AA/A Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 450,213
Baa/BBB Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 30,149
States and Political Subdivisions [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Balance | 40
Balance | 40
Amortized cost | 412,038
States and Political Subdivisions [Member] | AAA/AA/A Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 409,073
States and Political Subdivisions [Member] | Baa/BBB Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 2,965
Corporate Bonds [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Balance | 196
Provision for credit loss expense (benefit) | 18
Balance | 178
Amortized cost | 53,528
Corporate Bonds [Member] | AAA/AA/A Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 26,353
Corporate Bonds [Member] | Baa/BBB Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 27,175
U.S. Agency-Based Mortgage-Backed Securities [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 3,606
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 | 3,606
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 11,125
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 | 11,125
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 | 65
Asset-Backed Securities [Member] | AAA/AA/A Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | 56
Asset-Backed Securities [Member] | Baa/BBB Ratings [Member] |
Debt Securities Held To Maturity Credit Quality Indicator [Line Items] |
Amortized cost | $ 9

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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 -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aaa) -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447 + 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 -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447 + Details
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