Investments - Contractual Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Amortized Cost
Less: loaned securities	$ 103,996	$ 57,499
Debt Securities, Available-for-sale, Amortized Cost	5,367,729	5,393,623
Fair Value
Less: loaned securities	103,996	57,499
Fixed-maturities available for sale—at fair value, net of allowance for credit losses of $0 and $948 (amortized cost of $5,367,729 and $5,393,623)	5,517,078	5,723,340
Total fixed-maturities available for sale \| Non asset-backed securities
Amortized Cost
Due in one year or less	182,884
Due after one year through five years	1,116,102
Due after five years through 10 years	1,191,992
Due after 10 years	765,565
Fair Value
Due in one year or less	183,770
Due after one year through five years	1,150,676
Due after five years through 10 years	1,228,959
Due after 10 years	816,720
Total fixed-maturities available for sale \| Asset-backed and mortgage-backed securities
Amortized Cost
Asset-backed and mortgage-backed securities	2,174,355
Fair Value
Asset-backed and mortgage-backed securities	2,202,564
Total fixed-maturities available for sale \| Total fixed-maturities available for sale
Amortized Cost
Total	5,430,898	5,426,787
Debt Securities, Available-for-sale, Amortized Cost	5,367,729	5,393,623
Fair Value
Total	5,582,689	5,759,442
Fixed-maturities available for sale—at fair value, net of allowance for credit losses of $0 and $948 (amortized cost of $5,367,729 and $5,393,623)	5,517,078	5,723,340
Loaned securities, amortized cost \| Total fixed-maturities available for sale \| Total fixed-maturities available for sale
Amortized Cost
Less: loaned securities	63,169	33,164
Fair Value
Less: loaned securities	63,169	33,164
Loaned securities \| Total fixed-maturities available for sale
Amortized Cost
Less: loaned securities	65,600
Fair Value
Less: loaned securities	65,600
Loaned securities \| Total fixed-maturities available for sale \| Total fixed-maturities available for sale
Amortized Cost
Less: loaned securities	65,611	36,102
Fair Value
Less: loaned securities	$ 65,611	$ 36,102

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