Investments (Concentrations of Credit Risk) (Details) - Foreign government - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
JAPAN
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value, Concentration of Risk, Investments	$ 24,295	$ 32,723
Republic of Korea
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value, Concentration of Risk, Investments	5,887	$ 7,117
MEXICO
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value, Concentration of Risk, Investments	$ 3,463