Reinsurance - Effects of Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Premiums Earned, Net [Abstract]
Direct	$ 76,320	$ 69,711	$ 62,968
Assumed	492	478	2,108
Ceded	(680)	(825)	(1,954)
Net premiums	76,132	69,364	63,122
Policyholder Benefits and Claims Incurred, Net [Abstract]
Direct	64,414	56,077	52,592
Assumed	398	329	1,562
Ceded	(552)	(727)	(1,625)
Net benefit costs	$ 64,260	$ 55,679	$ 52,529