Investments (Mortgage Loans by Credit Quality Indicator) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 5,861	$ 5,727
Construction Loan	$ 12	$ 0
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]
Loans Receivable, Gross, Commercial, Real Estate	$ 5,531	$ 5,454
1.00x - 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	238	179
Less than 1.00x
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	80	94
0% - 59.99%
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	2,909	3,084
Construction Loan	$ 12	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	49.60%	53.80%
0% - 59.99% | Greater than 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 2,774	$ 3,025
0% - 59.99% | 1.00x - 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	106	52
0% - 59.99% | Less than 1.00x
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	17	7
60% - 69.99%
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	2,108	1,905
Construction Loan	$ 0	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	36.00%	33.30%
60% - 69.99% | Greater than 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 2,013	$ 1,841
60% - 69.99% | 1.00x - 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	62	53
60% - 69.99% | Less than 1.00x
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	33	11
70% - 79.99%
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	617	544
Construction Loan	$ 0	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	10.50%	9.50%
70% - 79.99% | Greater than 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 555	$ 492
70% - 79.99% | 1.00x - 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	49	13
70% - 79.99% | Less than 1.00x
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	13	39
Greater than 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	227	194
Construction Loan	$ 0	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	3.90%	3.40%
Greater than 80% | Greater than 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 189	$ 96
Greater than 80% | 1.00x - 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	21	61
Greater than 80% | Less than 1.00x
Financing Receivable, Credit Quality Indicator [Line Items]
Loans Receivable, Gross, Commercial, Real Estate	$ 17	$ 37