Quarterly Results of Operations (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 4,359	$ 4,043	$ 4,137	$ 4,119	$ 4,143	$ 3,643	$ 3,606	$ 3,204	$ 16,658	$ 14,596	$ 14,300
Total benefits and expenses	4,302	4,077	3,655	3,933	3,974	3,358	3,411	3,300	15,967	14,043	13,168
Income before income taxes	57	(34)	482	186	169	285	195	(96)	691	553	1,132
Net Income (Loss) Attributable to Parent	$ 156	$ (22)	$ 344	$ 139	$ 132	$ 213	$ 158	$ (88)	$ 617	$ 415	$ 870
Basic earnings per share:
Earnings Per Share, Basic (in dollars per share)	$ 2.32	$ (0.32)	$ 5.06	$ 2.04	$ 1.95	$ 3.13	$ 2.49	$ (1.41)	$ 9.10	$ 6.35	$ 13.88
Earnings Per Share, Diluted (in dollars per share)	$ 2.30	$ (0.32)	$ 5.02	$ 2.03	$ 1.94	$ 3.12	$ 2.48	$ (1.41)	$ 9.04	$ 6.31	$ 13.62