Investments (Commercial Mortgage Loans By Year Of Origination) (Details) $ in Millions	Mar. 31, 2020 USD ($) item	Dec. 31, 2019 USD ($)
Loan-to-value ratio, less than 65% [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 14,723	$ 14,206
Loan-to-value ratio, 65% to 74% [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	1,428	1,399
Commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	715
2019	3,457
2018	2,617
2017	2,000
2016	1,949
2015 and prior	5,414
Total	16,152	15,606
Commercial [Member] | Loan-to-value ratio, less than 65% [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	654
2019	2,964
2018	2,346
2017	1,798
2016	1,732
2015 and prior	5,229
Total	$ 14,723
2020 | item	3.57
2019 | item	2.29
2018 | item	2.17
2017 | item	2.34
2016 | item	2.37
2015 and prior | item	2.43
Commercial [Member] | Loan-to-value ratio, 65% to 74% [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 61
2019	493
2018	271
2017	202
2016	217
2015 and prior	184
Total	$ 1,428
2020 | item	1.47
2019 | item	1.78
2018 | item	1.48
2017 | item	2.67
2016 | item	1.92
2015 and prior | item	1.68
Commercial [Member] | 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