Supplementary Insurance Information - Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	$ 546	$ 1,037	$ 1,682
Reserves for future policy benefits, claims and unpaid losses and LAE	53,572	51,250	46,992
Unearned premiums	2,803	2,830	2,595
Net earned premiums	5,118	5,207	4,889
Net investment income	2,132	2,303	2,094
Benefits, claims, losses and settlement expenses	4,503	4,458	4,041
Amortization of deferred policy acquisition costs	866	923	860
Other operating expenses	1,692	1,748	1,610
Net written premiums (excluding life)	5,017	5,345	5,026
Property and casualty insurance
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	244	322	299
Reserves for future policy benefits, claims and unpaid losses and LAE	10,392	10,232	9,741
Unearned premiums	2,803	2,830	2,595
Net earned premiums	5,099	5,185	4,865
Net investment income	399	472	438
Benefits, claims, losses and settlement expenses	3,271	3,271	3,003
Amortization of deferred policy acquisition costs	615	721	644
Other operating expenses	1,036	1,027	957
Net written premiums (excluding life)	5,013	5,342	5,023
Annuity
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	287	696	1,360
Reserves for future policy benefits, claims and unpaid losses and LAE	42,573	40,406	36,616
Net investment income	1,699	1,792	1,638
Benefits, claims, losses and settlement expenses	1,192	1,151	998
Amortization of deferred policy acquisition costs	247	198	212
Other operating expenses	220	201	192
Other
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	15	19	23
Reserves for future policy benefits, claims and unpaid losses and LAE	607	612	635
Net earned premiums	19	22	24
Net investment income	34	39	18
Benefits, claims, losses and settlement expenses	40	36	40
Amortization of deferred policy acquisition costs	4	4	4
Other operating expenses	436	520	461
Net written premiums (excluding life)	$ 4	$ 3	$ 3