Investments - Carrying Values of Other Long-Term Investments (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Other long-term investments	$ 2,832
Other long-term investments		$ 2,403
Unfunded commitments	2,325
Real estate investments
Schedule of Investments [Line Items]
Other long-term investments	951
Other long-term investments		788
Unfunded commitments	677
Securities partnerships
Schedule of Investments [Line Items]
Other long-term investments	1,683
Other long-term investments		1,409
Unfunded commitments	1,617
Other
Schedule of Investments [Line Items]
Other long-term investments	198
Other long-term investments		$ 206
Unfunded commitments	$ 31