Schedule IV Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Net Amount	$ 28,523	$ 30,561	$ 30,614
Reportable Segments
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Percent of Amount Assumed to Net	24.70%	21.70%	15.30%
Direct	$ 32,977	$ 34,380	$ 34,939
Ceded to Other Companies	11,496	10,442	9,019
Assumed from Other Companies	7,042	6,623	4,694
Net Amount	$ 28,523	$ 30,561	$ 30,614
Reportable Segments | General Insurance Companies
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Percent of Amount Assumed to Net	24.80%	23.80%	16.60%
Direct	$ 28,596	$ 30,017	$ 31,450
Ceded to Other Companies	10,435	9,526	8,164
Assumed from Other Companies	5,984	6,395	4,638
Net Amount	$ 24,145	$ 26,886	$ 27,924
Reportable Segments | Life and Retirement Companies
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Percent of Amount Assumed to Net	24.20%	6.20%	2.10%
Direct	$ 4,381	$ 4,363	$ 3,489
Ceded to Other Companies	1,061	916	855
Assumed from Other Companies	1,058	228	56
Net Amount	$ 4,378	$ 3,675	$ 2,690
Long-duration insurance in force
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Percent of Amount Assumed to Net	0.00%	0.00%	0.00%
Direct	$ 1,243,389	$ 1,185,771	$ 1,094,774
Ceded to Other Companies	292,517	264,732	228,846
Assumed from Other Companies	225	279	300
Net Amount	$ 951,097	$ 921,318	$ 866,228