Investments (Amortized Cost and Fair Value of Fixed Maturities by Contractual Maturities) (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Amortized Cost
Due in one year or less	$ 404,018
Due after one year through five years	3,869,672
Due after five years through ten years	4,198,773
Due after ten years	5,961,282
Amortized Cost	16,197,708	$ 12,737,749
Fair Value
Due in one year or less	389,373
Due after one year through five years	3,619,474
Due after five years through ten years	3,645,235
Due after ten years	5,099,732
Fair Value	14,438,956	13,278,166
Asset-backed securities
Amortized Cost
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost	925,707
Fair Value
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value	894,553
Commercial mortgage-backed securities
Amortized Cost
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost	740,060
Fair Value
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value	694,688
Residential mortgage-backed securities
Amortized Cost
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost	98,196
Fair Value
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value	95,901
Fixed maturities
Amortized Cost
Amortized Cost	16,197,708	12,737,749
Fair Value
Fair Value	14,438,956	13,278,166
Fixed maturities \| Asset-backed securities
Amortized Cost
Amortized Cost	925,707	547,549
Fair Value
Fair Value	894,553	547,310
Fixed maturities \| Commercial mortgage-backed securities
Amortized Cost
Amortized Cost	740,060	552,653
Fair Value
Fair Value	694,688	575,184
Fixed maturities \| Residential mortgage-backed securities
Amortized Cost
Amortized Cost	98,196	18,684
Fair Value
Fair Value	$ 95,901	$ 20,180

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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