Investments (Limited Partnerships and Real Estate Joint Ventures) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Real Estate [Line Items]
Real Estate Investments, Joint Ventures	$ 2,405	$ 2,327
Equity Method Investments
Real Estate [Line Items]
Real Estate Investments, Joint Ventures	970	934
Limited partnership Fair Value Member
Real Estate [Line Items]
Real Estate Investments, Joint Ventures	726	683
Corporate Joint Venture
Real Estate [Line Items]
Real Estate Investments, Joint Ventures	655	661
Limited Partnership Cost Method
Real Estate [Line Items]
Real Estate Investments, Joint Ventures	$ 54	$ 49