Investments (Amortized Cost and Fair Value of Fixed Maturities by Contractual Maturities) (Details) - USD ($) $ in Thousands		Sep. 30, 2025	Dec. 31, 2024
Amortized Cost
Due in one year or less		$ 2,160,794
Due after one year through five years		15,709,371
Due after five years through ten years		11,729,956
Due after ten years		10,126,620
Amortized Cost		46,290,215	$ 36,980,933
Fair Value
Due in one year or less		2,138,289
Due after one year through five years		15,871,043
Due after five years through ten years		11,929,860
Due after ten years		9,172,998
Fair Value	[1]	45,686,539	34,986,160
Asset-backed securities
Amortized Cost
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost		4,706,213
Amortized Cost		4,706,213	3,728,073
Fair Value
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value		4,733,008
Fair Value		4,733,008	3,750,663
Commercial mortgage-backed securities
Amortized Cost
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost		1,304,368
Amortized Cost		1,304,368	944,652
Fair Value
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value		1,287,383
Fair Value		1,287,383	895,775
Residential mortgage-backed securities
Amortized Cost
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost		552,893
Amortized Cost		552,893	367,005
Fair Value
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value		553,958
Fair Value		$ 553,958	$ 356,072

[1] See Note 4 for details of balances associated with variable interest entities.