Investments (Credit Quality Indicator) (Details) - Mortgage loans $ in Millions	Mar. 31, 2020 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 60
2019	297
2018	115
2017	219
2016	85
Prior	265
Total	1,041
DSCR ≥1.6x | LTV less than 55%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	60
2019	32
2018	19
2017	92
2016	41
Prior	130
Total	374
DSCR ≥1.6x | LTV 55% to 65%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	32
2018	29
2017	55
2016	4
Prior	0
Total	120
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	0
Total	5
DSCR 1.2x - 1.6x | LTV less than 55%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	33
2018	10
2017	13
2016	16
Prior	126
Total	198
DSCR 1.2x - 1.6x | LTV 55% to 65%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	73
2018	32
2017	32
2016	0
Prior	0
Total	137
DSCR 1.2x - 1.6x | LTV greater than 65%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	85
2018	0
2017	0
2016	0
Prior	0
Total	85
DSCR ≤1.2 | LTV less than 55%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	1
2018	11
2017	27
2016	0
Prior	9
Total	48
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	22
2018	0
2017	0
2016	24
Prior	0
Total	$ 46