Schedule IV Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reportable Segments
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	$ 33,823	$ 35,258	$ 38,579
Ceded to Other Companies	8,605	8,342	8,350
Assumed from Other Companies	4,431	3,369	2,947
Net Amount	$ 29,649	$ 30,285	$ 33,176
Percent of Amount Assumed to Net	14.90%	11.10%	8.90%
Reportable Segments | General Insurance Companies
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	$ 30,335	$ 30,205	$ 33,970
Ceded to Other Companies	7,755	7,533	7,561
Assumed from Other Companies	4,026	3,084	2,824
Net Amount	$ 26,606	$ 25,756	$ 29,233
Percent of Amount Assumed to Net	15.10%	12.00%	9.70%
Reportable Segments | Life and Retirement Companies
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	$ 3,488	$ 5,053	$ 4,609
Ceded to Other Companies	850	809	789
Assumed from Other Companies	405	285	123
Net Amount	$ 3,043	$ 4,529	$ 3,943
Percent of Amount Assumed to Net	13.30%	6.30%	3.10%
Reportable Segments | Other
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	$ 0	$ 0	$ 0
Ceded to Other Companies	0	0	0
Assumed from Other Companies	0	0	0
Net Amount	$ 0	$ 0	$ 0
Percent of Amount Assumed to Net	0.00%	0.00%	0.00%
Long-duration insurance in force
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	$ 1,094,774	$ 1,061,095	$ 1,025,653
Ceded to Other Companies	228,846	202,402	174,363
Assumed from Other Companies	300	321	339
Net Amount	$ 866,228	$ 859,014	$ 851,629
Percent of Amount Assumed to Net	0.00%	0.00%	0.00%