Investment Information - Maturity profile of available for sale securities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Estimated Fair Value:
Estimated fair value	$ 25,616	$ 21,015
Amortized Cost:
Amortized cost	26,195	22,615
Fixed maturities available for sale, at fair value
Estimated Fair Value:
Due in one year or less	480	511
Due after one year through five years	12,924	11,016
Due after five years through 10 years	5,249	3,984
Due after 10 years	334	403
Single maturity date	18,987	15,914
Estimated fair value	23,553	19,683
Amortized Cost:
Due in one year or less	499	537
Due after one year through five years	13,101	11,715
Due after five years through 10 years	5,450	4,527
Due after 10 years	374	480
Single maturity date	19,424	17,259
Amortized cost	24,131	21,282
Mortgage backed securities
Estimated Fair Value:
Securities without single maturity date	1,103	795
Estimated fair value	1,103	795
Amortized Cost:
Securities without single maturity date	1,162	877
Amortized cost	1,162	877
Commercial mortgage backed securities
Estimated Fair Value:
Securities without single maturity date	1,213	1,047
Estimated fair value	1,213	1,047
Amortized Cost:
Securities without single maturity date	1,246	1,107
Amortized cost	1,246	1,107
Asset backed securities
Estimated Fair Value:
Securities without single maturity date	2,250	1,927
Estimated fair value	2,250	1,927
Amortized Cost:
Securities without single maturity date	2,299	2,039
Amortized cost	$ 2,299	$ 2,039