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Schedule I - Summary of Investments - Other Than Investments in Related Parties (Details) $ in Thousands | Dec. 31, 2023 USD ($)
--- | ---
Amortized Cost or Cost | $ 9,071,424
Carrying Amount | 8,693,729
Short-term Investments [Member] |
Amortized Cost or Cost | 309,300
Carrying Amount | 309,317
Other Investments [Member] |
Amortized Cost or Cost | 91,164
Carrying Amount | 91,164
Alternative Investments [Member] |
Amortized Cost or Cost | 395,779
Carrying Amount | 395,779
Held-to-maturity Securities [Member] | All other corporate securities |
Amortized Cost or Cost | 22,700
Fair Value | 21,923
Carrying Amount | 22,700
Held-to-maturity Securities [Member] | Fixed Income Securities [Member] |
Amortized Cost or Cost | 22,700
Fair Value | 21,923
Carrying Amount | 22,700
AFS Fixed Income Securities [Member] | US Government Agencies Debt Securities [Member] |
Amortized Cost or Cost | 223,157
Fair Value | 205,035
Carrying Amount | 205,035
AFS Fixed Income Securities [Member] | Foreign Government |
Amortized Cost or Cost | 11,140
Fair Value | 9,803
Carrying Amount | 9,803
AFS Fixed Income Securities [Member] | Obligations of States and Political Subdivisions [Member] |
Amortized Cost or Cost | 612,938
Fair Value | 585,965
Carrying Amount | 585,965
AFS Fixed Income Securities [Member] | Public Utilities |
Amortized Cost or Cost | 150,064
Fair Value | 142,425
Carrying Amount | 142,425
AFS Fixed Income Securities [Member] | All other corporate securities |
Amortized Cost or Cost | 2,683,984
Fair Value | 2,568,814
Carrying Amount | 2,568,814
AFS Fixed Income Securities [Member] | CLO and Other ABS |
Amortized Cost or Cost | 1,911,831
Fair Value | 1,834,827
Carrying Amount | 1,834,827
AFS Fixed Income Securities [Member] | Commercial Mortgage-backed Securities (CMBS) [Member] |
Amortized Cost or Cost | 1,568,960
Fair Value | 1,477,483
Carrying Amount | 1,477,483
AFS Fixed Income Securities [Member] | Residential Mortgage Backed Securities [Member] |
Amortized Cost or Cost | 718,623
Fair Value | 674,845
Carrying Amount | 674,845
AFS Fixed Income Securities [Member] | Fixed Income Securities [Member] |
Amortized Cost or Cost | 7,880,697
Fair Value | 7,499,197
Carrying Amount | 7,499,197
Equity Securities [Member] | Banks, trusts, and insurance companies |
Amortized Cost or Cost | 33,224
Fair Value | 32,725
Carrying Amount | 32,725
Equity Securities [Member] | Industrial, miscellaneous and all other |
Amortized Cost or Cost | 147,892
Fair Value | 152,614
Carrying Amount | 152,614
Equity Securities [Member] | Preferred Stock [Member] |
Amortized Cost or Cost | 1,960
Fair Value | 1,816
Carrying Amount | 1,816
Equity Securities [Member] | Equity Securities [Member] |
Amortized Cost or Cost | 183,076
Fair Value | 187,155
Carrying Amount | 187,155
Commercial Mortgage Loans [Member] |
Amortized Cost or Cost | 188,708
Carrying Amount | $ 188,417

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