Reinsurance (Effect of Reinsurance on Life Insurance In Force) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reinsurance Disclosures [Abstract]
Reinsurance Premiums for Insurance Companies, by Product Segment, Gross Amount	$ 1,363	$ 1,462	$ 1,576
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Assumed from Other Companies	3,329,181	3,297,275	3,062,525
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	186,172	205,529	214,727
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 3,144,372	$ 3,093,208	$ 2,849,374
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	105.90%	106.60%	107.50%