Investments (Past Due Mortgage Loans by Portfolio Segment) (Details) - Mortgage Loans - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, current	$ 15,770
Financing receivable, before allowance for credit losses	15,883	$ 15,817
30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, past due	54
60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, past due	29
90 to 179 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, past due	12
180 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, past due	18
Commercial
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, current	9,715
Financing receivable, before allowance for credit losses	9,715	9,721
Commercial | 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, past due	0
Commercial | 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, past due	0
Commercial | 90 to 179 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, past due	0
Commercial | 180 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, past due	0
Agricultural
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, current	3,350
Financing receivable, before allowance for credit losses	3,361	3,388
Agricultural | 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, past due	0
Agricultural | 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, past due	10
Agricultural | 90 to 179 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, past due	0
Agricultural | 180 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, past due	1
Residential
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, current	2,705
Financing receivable, before allowance for credit losses	2,807	$ 2,708
Residential | 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, past due	54
Residential | 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, past due	19
Residential | 90 to 179 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, past due	12
Residential | 180 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable before allowance for credit losses, past due	$ 17