Reinsurance (Effect of Reinsurance on Life Insurance In Force) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reinsurance Disclosures [Abstract]
Reinsurance Premiums for Insurance Companies, by Product Segment, Gross Amount	$ 1,316	$ 1,363	$ 1,462
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Assumed from Other Companies	3,480,206	3,329,181	3,297,275
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	192,864	186,172	205,529
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 3,288,658	$ 3,144,372	$ 3,093,208
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	105.80%	105.90%	106.60%