Investments (Commercial Mortgage Loans By Year Of Origination) (Details) - Commercial [Member] $ in Millions	Mar. 31, 2020 USD ($) item	Dec. 31, 2019 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 706
2019	3,412
2018	2,610
2017	1,992
2016	1,947
2015 and prior	5,383
Total	16,050	$ 15,511
Loan-to-value ratio, less than 65% [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	645
2019	2,920
2018	2,343
2017	1,790
2016	1,730
2015 and prior	5,204
Total	$ 14,632	14,121
2020 | item	3.56
2019 | item	2.28
2018 | item	2.17
2017 | item	2.34
2016 | item	2.38
2015 and prior | item	2.44
Loan-to-value ratio, 65% to 74% [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 61
2019	492
2018	267
2017	202
2016	217
2015 and prior	178
Total	$ 1,417	1,389
2020 | item	1.47
2019 | item	1.78
2018 | item	1.48
2017 | item	2.67
2016 | item	1.92
2015 and prior | item	1.71
Loan-to-value ratio, 75% to 100% [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2015 and prior	$ 1
Total	$ 1	$ 1
2015 and prior | item	0.90