Investments - Carrying Values of Other Long-Term Investments (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Other long-term investments	$ 3,429	$ 2,832
Real estate investments
Schedule of Investments [Line Items]
Other long-term investments	1,161	951
Securities partnerships
Schedule of Investments [Line Items]
Other long-term investments	2,098	1,737
Other
Schedule of Investments [Line Items]
Other long-term investments	$ 170	$ 144