Investments - Contractual Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Amortized Cost
Less: loaned securities	$ 141,614	$ 203,693
Fixed-maturities available for sale, amortized cost	5,583,574	5,599,111
Fair Value
Less: loaned securities	141,614	203,693
Total fixed-maturities available for sale, Fair Value	5,292,480	5,188,228
Non asset-backed securities
Amortized Cost
Due in one year or less	111,757
Due after one year through five years	1,178,043
Due after five years through 10 years	965,508
Due after 10 years	936,054
Fair Value
Due in one year or less	110,762
Due after one year through five years	1,152,612
Due after five years through 10 years	920,061
Due after 10 years	787,994
Asset-backed and mortgage-backed securities
Amortized Cost
Asset-backed and mortgage-backed securities	2,519,593
Fair Value
Asset-backed and mortgage-backed securities	2,443,990
Total fixed-maturities available for sale
Amortized Cost
Total	5,710,955	5,734,767
Fixed-maturities available for sale, amortized cost	5,583,574	5,599,111
Fair Value
Total	5,415,419	5,315,410
Total fixed-maturities available for sale, Fair Value	5,292,480	5,188,228
Fixed-maturities available for sale \| Total fixed-maturities available for sale
Amortized Cost
Total	5,710,955
Fair Value
Total	5,415,419
Loaned securities, amortized cost \| Total fixed-maturities available for sale
Amortized Cost
Less: loaned securities	127,381	135,656
Fair Value
Less: loaned securities	127,381	135,656
Loaned securities, fair value \| Total fixed-maturities available for sale
Amortized Cost
Less: loaned securities	122,939	127,182
Fair Value
Less: loaned securities	$ 122,939	$ 127,182

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