Investments - Equity Security Investments (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Cost
Equity securities with readily determinable fair values	$ 203	$ 180
Equity securities with no readily determinable fair value	227	225
Hybrid equity securities	57	58
Total	487	463
Carrying Value
Equity securities with readily determinable fair values	180	202
Equity securities with no readily determinable fair value	332	255
Hybrid equity securities	39	44
Total	$ 551	$ 501