Investments (Current and Long-term Equity Securities) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Marketable Securities [Line Items]
Equity Securities	$ 3,075	$ 1,009
Exchange Traded Funds [Member]
Marketable Securities [Line Items]
Equity Securities	2,646	44
Fixed Maturity Mutual Funds [Member]
Marketable Securities [Line Items]
Equity Securities	143	643
Common Equity Securities [Member]
Marketable Securities [Line Items]
Equity Securities	225	237
Private Equity Funds [Member]
Marketable Securities [Line Items]
Equity Securities	$ 61	$ 85