Reinsurance (Effect of Reinsurance on Life Insurance In Force) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reinsurance Disclosures [Abstract]
Reinsurance Premiums for Insurance Companies, by Product Segment, Gross Amount	$ 1,990	$ 1,316	$ 1,363
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Assumed from Other Companies	3,480,692	3,480,206	3,329,181
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	184,625	192,864	186,172
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 3,298,057	$ 3,288,658	$ 3,144,372
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	105.50%	105.80%	105.90%