Investments (Concentrations of Credit Risk - Narrative) (Details) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Securities holdings exposure in single issuer greater than stated percentage of Company's equity	10.00%	10.00%	10.00%
Japan | Foreign government
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Government and agency fixed maturity securities	$ 35.8	$ 33.7
Republic of Korea | Foreign government
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Government and agency fixed maturity securities	$ 8.0	$ 7.3