Investment Information - Maturity profile of available for sale securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Estimated Fair Value
Due in one year or less	$ 579,231	$ 300,889
Due after one year through five years	10,029,151	8,355,255
Due after five years through 10 years	3,856,180	4,689,155
Due after 10 years	239,008	505,758
Single maturity date	14,703,570	13,851,057
Estimated Fair Value	20,061,584	19,732,825
Amortized Cost
Due in one year or less	599,970	299,772
Due after one year through five years	10,808,495	8,339,387
Due after five years through 10 years	4,495,113	4,684,393
Due after 10 years	356,289	493,927
Single maturity date	16,259,867	13,817,479
Cost or Amortized Cost	21,854,126	19,708,561
Fixed maturities
Estimated Fair Value
Estimated Fair Value	18,120,727	17,998,109
Amortized Cost
Cost or Amortized Cost	19,913,055	17,973,823
Mortgage backed securities
Estimated Fair Value
Securities without single maturity date	763,371	408,477
Estimated Fair Value	763,371	408,477
Amortized Cost
Securities without single maturity date	839,991	411,110
Cost or Amortized Cost	839,991	411,110
Commercial mortgage backed securities
Estimated Fair Value
Securities without single maturity date	1,064,238	1,046,484
Estimated Fair Value	1,064,238	1,046,484
Amortized Cost
Securities without single maturity date	1,112,752	1,047,867
Cost or Amortized Cost	1,112,752	1,047,867
Asset backed securities
Estimated Fair Value
Securities without single maturity date	1,589,548	2,692,091
Estimated Fair Value	1,589,548	2,692,091
Amortized Cost
Securities without single maturity date	1,700,445	2,697,367
Cost or Amortized Cost	$ 1,700,445	$ 2,697,367