Investments, Debt and Equity Securities (Age Analysis of Past Due Recorded Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	$ 15	$ 0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		5,727
Loans Receivable, Gross, Commercial, Real Estate	5,861	5,727
Commercial Real Estate Portfolio Segment
Financing Receivable, Past Due [Line Items]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	5,846
Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	$ 15	$ 0