Investments (Credit Quality Indicator) (Details) - Mortgage loans $ in Millions	Sep. 30, 2020 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 143
2019	296
2018	104
2017	222
2016	85
Prior	259
Total	1,109
DSCR ≥1.6x | LTV less than 55%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	75
2019	33
2018	19
2017	85
2016	33
Prior	161
Total	406
DSCR ≥1.6x | LTV 55% to 65%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	33
2018	29
2017	55
2016	12
Prior	0
Total	129
DSCR ≥1.6x | LTV greater than 65%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	5
2018	0
2017	0
2016	0
Prior	12
Total	17
DSCR 1.2x - 1.6x | LTV less than 55%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	31
2018	10
2017	13
2016	16
Prior	79
Total	149
DSCR 1.2x - 1.6x | LTV 55% to 65%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	20
2019	54
2018	32
2017	24
2016	0
Prior	0
Total	130
DSCR 1.2x - 1.6x | LTV greater than 65%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	48
2019	103
2018	0
2017	0
2016	0
Prior	0
Total	151
DSCR ≤1.2 | LTV less than 55%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Total	0
DSCR ≤1.2 | LTV 55% to 65%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	14
2018	14
2017	0
2016	0
Prior	0
Total	28
DSCR ≤1.2 | LTV greater than 65%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	23
2018	0
2017	45
2016	24
Prior	7
Total	$ 99