Investments (Commercial Mortgage Loans By Year Of Origination) (Details) - Commercial [Member] $ in Millions	Sep. 30, 2020 USD ($) item	Dec. 31, 2019 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 1,045
2019	3,424
2018	2,595
2017	1,974
2016	1,923
2015 and prior	5,025
Total	15,986	$ 15,606
Loan-to-value ratio, less than 65% [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	960
2019	2,976
2018	2,371
2017	1,804
2016	1,691
2015 and prior	4,877
Total	$ 14,679	14,206
2020 | item	3.30
2019 | item	2.31
2018 | item	2.22
2017 | item	2.34
2016 | item	2.44
2015 and prior | item	2.47
Loan-to-value ratio, 65% to 74% [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 85
2019	448
2018	224
2017	170
2016	204
2015 and prior	140
Total	$ 1,271	1,399
2020 | item	1.67
2019 | item	1.74
2018 | item	1.53
2017 | item	2.62
2016 | item	1.62
2015 and prior | item	1.89
Loan-to-value ratio, 75% to 100% [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2016	$ 28
2015 and prior	8
Total	$ 36	$ 1
2016 | item	1.30
2015 and prior | item	1.03