Investments - Contractual Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Amortized Cost
Amortized Cost	$ 5,732,454
Loaned securities	130,369	$ 112,139
Fixed-maturities available for sale, amortized cost	5,655,280	5,587,261
Fair Value
Fair Value	5,242,487
Loaned securities	130,369	112,139
Total fixed-maturities available for sale, Fair Value	5,172,375	5,017,711
Non asset-backed securities
Amortized Cost
Due in one year or less	112,649
Due after one year through five years	1,296,849
Due after five years through 10 years	992,330
Due after 10 years	878,999
Fair Value
Due in one year or less	110,871
Due after one year through five years	1,226,557
Due after five years through 10 years	887,695
Due after 10 years	716,055
Asset-backed and mortgage-backed securities
Amortized Cost
Asset-backed and mortgage-backed securities	2,451,627
Fair Value
Asset-backed and mortgage-backed securities	2,301,309
Total fixed-maturities available for sale
Amortized Cost
Fixed-maturities available for sale, amortized cost	5,655,280	5,587,261
Fair Value
Total fixed-maturities available for sale, Fair Value	5,172,375	$ 5,017,711
Loaned securities, amortized cost
Amortized Cost
Loaned securities	77,174
Fair Value
Loaned securities	77,174
Loaned securities, fair value
Amortized Cost
Loaned securities	70,112
Fair Value
Loaned securities	$ 70,112

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