Investments (Rollforward of the Allowance for Credit Losses for Mortgage Loans by Portfolio Segment) (Details) - Mortgage Loans $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of year	$ 64
Current period provision	30
Financing receivable, allowance for credit losses, end of year	94
Cumulative Effect, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of year	0
Cumulative Effect, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of year	64
Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of year	47
Current period provision	17
Financing receivable, allowance for credit losses, end of year	44
Commercial | Cumulative Effect, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of year	(20)
Commercial | Cumulative Effect, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of year	27
Agricultural
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of year	10
Current period provision	(1)
Financing receivable, allowance for credit losses, end of year	15
Agricultural | Cumulative Effect, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of year	6
Agricultural | Cumulative Effect, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of year	16
Residential
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of year	7
Current period provision	14
Financing receivable, allowance for credit losses, end of year	35
Residential | Cumulative Effect, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of year	14
Residential | Cumulative Effect, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing receivable, allowance for credit losses, beginning of year	$ 21