Investments (Mortgage Loans by Credit Quality Indicator) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 5,981	$ 5,727
Loans Receivable, Gross, Commercial, Construction	$ 4	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	100.00%	100.00%
LTV 0 to 59 Percent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 3,044	$ 3,084
Loans Receivable, Gross, Commercial, Construction	$ 4	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	50.90%	53.80%
LTV 60 To 69 Percent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 2,043	$ 1,905
Loans Receivable, Gross, Commercial, Construction	$ 0	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	34.20%	33.30%
LTV 70 To 79 Percent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 675	$ 544
Loans Receivable, Gross, Commercial, Construction	$ 0	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	11.30%	9.50%
Debt-to-Value Ratio, 80 to 100 Percent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 219	$ 194
Loans Receivable, Gross, Commercial, Construction	$ 0	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	3.60%	3.40%
Debt Service Coverage Ratio Range One [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 5,610	$ 5,454
Debt Service Coverage Ratio Range One [Member] | LTV 0 to 59 Percent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,884	3,025
Debt Service Coverage Ratio Range One [Member] | LTV 60 To 69 Percent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,965	1,841
Debt Service Coverage Ratio Range One [Member] | LTV 70 To 79 Percent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	581	492
Debt Service Coverage Ratio Range One [Member] | Debt-to-Value Ratio, 80 to 100 Percent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	180	96
Debt Service Coverage Ratio Range Two [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	274	179
Debt Service Coverage Ratio Range Two [Member] | LTV 0 to 59 Percent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	137	52
Debt Service Coverage Ratio Range Two [Member] | LTV 60 To 69 Percent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	48	53
Debt Service Coverage Ratio Range Two [Member] | LTV 70 To 79 Percent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	67	13
Debt Service Coverage Ratio Range Two [Member] | Debt-to-Value Ratio, 80 to 100 Percent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	22	61
Debt Service Coverage Ratio Range Three [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	93	94
Debt Service Coverage Ratio Range Three [Member] | LTV 0 to 59 Percent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	19	7
Debt Service Coverage Ratio Range Three [Member] | LTV 60 To 69 Percent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	30	11
Debt Service Coverage Ratio Range Three [Member] | LTV 70 To 79 Percent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	27	39
Debt Service Coverage Ratio Range Three [Member] | Debt-to-Value Ratio, 80 to 100 Percent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 17	$ 37