Investments (Amortized Cost and Fair Value of Fixed Maturity Holdings by Industry Type) (Details) - Corporate Debt Securities [Member] - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Corporate Securities by Investment Sector And Credit Rating [Line Items]
Amortized Cost	$ 33,687	$ 31,963
Estimated Fair Value	$ 37,004	$ 36,208
% of Total	100.00%	100.00%
Financial Services Sector [Member]
Corporate Securities by Investment Sector And Credit Rating [Line Items]
Amortized Cost	$ 12,479	$ 11,785
Estimated Fair Value	$ 13,627	$ 13,236
% of Total	36.80%	36.60%
Commercial and Industrial Sector [Member]
Corporate Securities by Investment Sector And Credit Rating [Line Items]
Amortized Cost	$ 17,032	$ 16,274
Estimated Fair Value	$ 18,749	$ 18,435
% of Total	50.70%	50.90%
Utility Sector [Member]
Corporate Securities by Investment Sector And Credit Rating [Line Items]
Amortized Cost	$ 4,176	$ 3,904
Estimated Fair Value	$ 4,628	$ 4,537
% of Total	12.50%	12.50%