Policyholders' Liabilities (Future Policy Benefits) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Liability for Future Policy Benefits and Unpaid Claims and Claims Adjustment Expense [Abstract]
Life insurance	$ 191,654	$ 180,749
Individual and group annuities and supplementary contracts	75,940	72,624
Other contract liabilities	23,052	17,665
Subtotal future policy benefits excluding unpaid claims and claim settlement expenses	290,646	271,038
Unpaid claims and claim settlement expenses	2,881	2,808
Total future policy benefits	$ 293,527	$ 273,846