Investments - Contractual Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Amortized Cost
Loaned securities	$ 119,837	$ 203,693
Fixed-maturities available for sale, amortized cost	5,657,808	5,599,111
Fair Value
Loaned securities	119,837	203,693
Total fixed-maturities available for sale, Fair Value	5,209,025	5,188,228
Total fixed-maturities available for sale
Amortized Cost
Total	5,774,322	5,734,767
Fixed-maturities available for sale, amortized cost	5,657,808	5,599,111
Fair Value
Total	5,314,994	5,315,410
Total fixed-maturities available for sale, Fair Value	5,209,025	5,188,228
Total fixed-maturities available for sale \| Fixed-maturities available for sale
Amortized Cost
Total	5,774,322
Fixed-maturities available for sale, amortized cost	5,657,808
Fair Value
Total	5,314,994
Total fixed-maturities available for sale, Fair Value	5,209,025
Non asset-backed securities
Amortized Cost
Due in one year or less	107,336
Due after one year through five years	1,243,833
Due after five years through 10 years	994,198
Due after 10 years	880,824
Fair Value
Due in one year or less	105,965
Due after one year through five years	1,187,261
Due after five years through 10 years	907,708
Due after 10 years	703,394
Asset-backed and mortgage-backed securities
Amortized Cost
Asset-backed and mortgage-backed securities	2,548,131
Fair Value
Asset-backed and mortgage-backed securities	2,410,666
Loaned securities, amortized cost \| Total fixed-maturities available for sale
Amortized Cost
Loaned securities	116,514	135,656
Fair Value
Loaned securities	116,514	135,656
Loaned securities, fair value \| Total fixed-maturities available for sale
Amortized Cost
Loaned securities	105,969	127,182
Fair Value
Loaned securities	$ 105,969	$ 127,182

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