Investments (Current Equity Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Marketable Securities [Line Items]
Equity Securities	$ 1,559	$ 1,009
Exchange Traded Funds [Member]
Marketable Securities [Line Items]
Equity Securities	1,154	44
Fixed Maturity Mutual Funds [Member]
Marketable Securities [Line Items]
Equity Securities	144	643
Common Equity Securities [Member]
Marketable Securities [Line Items]
Equity Securities	201	237
Private Equity Funds [Member]
Marketable Securities [Line Items]
Equity Securities	$ 60	$ 85