Investments - Loans Segregated By Risk Rating (Details) $ in Millions	Sep. 30, 2020 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Total non-accrual loans	$ 64
Residential Portfolio Segment
Financing Receivable, Credit Quality Indicator [Line Items]
2020	270
2019	639
2018	74
2017	47
2016	64
Prior	2
Total	1,096
Total non-accrual loans	64
Residential Portfolio Segment | Current (less than 30 days past due)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	244
2019	536
2018	66
2017	46
2016	62
Prior	2
Total	956
Residential Portfolio Segment | 30-89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
2020	17
2019	74
2018	5
2017	1
2016	2
Prior	0
Total	99
Residential Portfolio Segment | Over 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
2020	9
2019	29
2018	3
2017	0
2016	0
Prior	0
Total	41
Commercial Portfolio Segment
Financing Receivable, Credit Quality Indicator [Line Items]
2020	174
2019	0
2018	6
2017	0
2016	11
Prior	355
Total	546
Total non-accrual loans	0
Commercial Portfolio Segment | Greater than 1.25
Financing Receivable, Credit Quality Indicator [Line Items]
2020	174
2019	0
2018	6
2017	0
2016	11
Prior	349
Total	540
Commercial Portfolio Segment | Greater than 1.00 but less than 1.25
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	6
Total	6
Commercial Portfolio Segment | Less than 1.00
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Total	0
Commercial Portfolio Segment | Less than 50%
Financing Receivable, Credit Quality Indicator [Line Items]
2020	107
2019	0
2018	6
2017	0
2016	0
Prior	306
Total	419
Commercial Portfolio Segment | LTV 50 to 60 Percent
Financing Receivable, Credit Quality Indicator [Line Items]
2020	34
2019	0
2018	0
2017	0
2016	11
Prior	49
Total	94
Commercial Portfolio Segment | LTV 60 to 75 Percent
Financing Receivable, Credit Quality Indicator [Line Items]
2020	33
2019	0
2018	0
2017	0
2016	0
Prior	0
Total	33
Commercial Portfolio Segment | Current (less than 30 days past due)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	174
2019	0
2018	6
2017	0
2016	11
Prior	355
Total	546
Commercial Portfolio Segment | 30-89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Total	0
Commercial Portfolio Segment | Over 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Total	$ 0