Supplementary Insurance Information - Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	$ 1,037	$ 1,682	$ 1,216
Reserves for future policy benefits, claims and unpaid losses and LAE	51,250	46,992	43,652
Unearned premiums	2,830	2,595	2,410
Net earned premiums	5,207	4,889	4,601
Net investment income	2,303	2,094	1,831
Benefits, claims, losses and settlement expenses	4,458	4,041	3,873
Amortization of deferred policy acquisition costs	923	860	690
Other operating expenses	1,748	1,610	1,578
Net written premiums (excluding life)	5,345	5,026	4,754
Property and casualty insurance
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	322	299	270
Reserves for future policy benefits, claims and unpaid losses and LAE	10,232	9,741	9,678
Unearned premiums	2,830	2,595	2,410
Net earned premiums	5,185	4,865	4,579
Net investment income	472	438	362
Benefits, claims, losses and settlement expenses	3,271	3,003	2,955
Amortization of deferred policy acquisition costs	721	644	556
Other operating expenses	1,027	957	867
Net written premiums (excluding life)	5,342	5,023	4,751
Annuity
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	696	1,360	920
Reserves for future policy benefits, claims and unpaid losses and LAE	40,406	36,616	33,316
Net investment income	1,792	1,638	1,458
Benefits, claims, losses and settlement expenses	1,151	998	892
Amortization of deferred policy acquisition costs	198	212	130
Other operating expenses	189	174	159
Other
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	19	23	26
Reserves for future policy benefits, claims and unpaid losses and LAE	612	635	658
Net earned premiums	22	24	22
Net investment income	39	18	11
Benefits, claims, losses and settlement expenses	36	40	26
Amortization of deferred policy acquisition costs	4	4	4
Other operating expenses	532	479	552
Net written premiums (excluding life)	$ 3	$ 3	$ 3