Investments (Mortgage Loans by Credit Quality Indicator) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 5,727	$ 4,983
Construction Loan	$ 0	$ 33
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	100.00%	100.00%
Greater than 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 5,454	$ 4,561
1.00x - 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	179	233
Less than 1.00x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	94	156
0% - 59.99%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,084	2,524
Construction Loan	$ 0	$ 14
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	53.80%	50.60%
0% - 59.99% | Greater than 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 3,025	$ 2,411
0% - 59.99% | 1.00x - 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	52	61
0% - 59.99% | Less than 1.00x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	7	38
60% - 69.99%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,905	1,749
Construction Loan	$ 0	$ 19
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	33.30%	35.10%
60% - 69.99% | Greater than 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 1,841	$ 1,618
60% - 69.99% | 1.00x - 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	53	74
60% - 69.99% | Less than 1.00x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	11	38
70% - 79.99%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	544	516
Construction Loan	$ 0	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	9.50%	10.40%
70% - 79.99% | Greater than 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 492	$ 414
70% - 79.99% | 1.00x - 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	13	48
70% - 79.99% | Less than 1.00x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	39	54
Greater than 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	194	194
Construction Loan	$ 0	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	3.40%	3.90%
Greater than 80% | Greater than 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 96	$ 118
Greater than 80% | 1.00x - 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	61	50
Greater than 80% | Less than 1.00x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 37	$ 26