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Fair Value Measurements - Quantitative Information of Our Financial Assets and Liabilities That Were Disclosed at Fair Value (Details) - USD ($) $ in Thousands | Mar. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed income securities, held-to-maturity - fair value | $ 19,183 | $ 21,923
Commercial mortgage loans, fair value | 197,807 | 178,913
Long-term debt, fair value | 497,298 | 503,805
Corporate securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed income securities, held-to-maturity - fair value | 19,183 | 21,923
Quoted Prices in  Active Markets for Identical Assets/ Liabilities (Level 1) |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed income securities, held-to-maturity - fair value | 0 | 0
Commercial mortgage loans, fair value | 0 | 0
Long-term debt, fair value | 0 | 0
Quoted Prices in  Active Markets for Identical Assets/ Liabilities (Level 1) | Corporate securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed income securities, held-to-maturity - fair value | 0 | 0
Significant Other Observable Inputs (Level 2) |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed income securities, held-to-maturity - fair value | 19,183 | 21,923
Commercial mortgage loans, fair value | 0 | 0
Long-term debt, fair value | 497,298 | 503,805
Significant Other Observable Inputs (Level 2) | Corporate securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed income securities, held-to-maturity - fair value | 19,183 | 21,923
Significant Unobservable Inputs (Level 3) |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed income securities, held-to-maturity - fair value | 0 | 0
Commercial mortgage loans, fair value | 197,807 | 178,913
Long-term debt, fair value | 0 | 0
Significant Unobservable Inputs (Level 3) | Corporate securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed income securities, held-to-maturity - fair value | 0 | 0
7.25% Senior Notes |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term debt, fair value | 51,137 | 53,047
7.25% Senior Notes | Quoted Prices in  Active Markets for Identical Assets/ Liabilities (Level 1) |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term debt, fair value | 0 | 0
7.25% Senior Notes | Significant Other Observable Inputs (Level 2) |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term debt, fair value | 51,137 | 53,047
7.25% Senior Notes | Significant Unobservable Inputs (Level 3) |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term debt, fair value | 0 | 0
6.70% Senior Notes |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term debt, fair value | 101,666 | 104,039
6.70% Senior Notes | Quoted Prices in  Active Markets for Identical Assets/ Liabilities (Level 1) |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term debt, fair value | 0 | 0
6.70% Senior Notes | Significant Other Observable Inputs (Level 2) |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term debt, fair value | 101,666 | 104,039
6.70% Senior Notes | Significant Unobservable Inputs (Level 3) |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term debt, fair value | 0 | 0
5.375% Senior Notes |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term debt, fair value | 286,927 | 288,787
5.375% Senior Notes | Quoted Prices in  Active Markets for Identical Assets/ Liabilities (Level 1) |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term debt, fair value | 0 | 0
5.375% Senior Notes | Significant Other Observable Inputs (Level 2) |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term debt, fair value | 286,927 | 288,787
5.375% Senior Notes | Significant Unobservable Inputs (Level 3) |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term debt, fair value | 0 | 0
3.03% borrowings from FHLBI |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term debt, fair value | 57,568 | 57,932
3.03% borrowings from FHLBI | Quoted Prices in  Active Markets for Identical Assets/ Liabilities (Level 1) |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term debt, fair value | 0 | 0
3.03% borrowings from FHLBI | Significant Other Observable Inputs (Level 2) |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term debt, fair value | 57,568 | 57,932
3.03% borrowings from FHLBI | Significant Unobservable Inputs (Level 3) |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term debt, fair value | $ 0 | $ 0

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