Investments (Rollforward of the Allowance for Credit Losses for Mortgage Loans by Portfolio Segment) (Details) - Mortgage Loans $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of period	$ 64
Current period provision	4
Financing receivable, allowance for credit losses, end of period	68
Cumulative Effect, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of period	0
Cumulative Effect, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of period	64
Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of period	47
Current period provision	0
Financing receivable, allowance for credit losses, end of period	27
Commercial | Cumulative Effect, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of period	(20)
Commercial | Cumulative Effect, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of period	27
Agricultural
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of period	10
Current period provision	1
Financing receivable, allowance for credit losses, end of period	17
Agricultural | Cumulative Effect, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of period	6
Agricultural | Cumulative Effect, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of period	16
Residential
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of period	7
Current period provision	3
Financing receivable, allowance for credit losses, end of period	24
Residential | Cumulative Effect, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of period	14
Residential | Cumulative Effect, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of period	$ 21