Investments - Loans by Loan to Value (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Mar. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		$ 4,670	$ 4,664
Targeted maximum amount of mortgage loans lended, percent of estimated fair value of underlying real estate		75.00%
Benchmark loan to value ratio, greater than indicates unpaid loan amount exceeds underlying collateral	100.00%	100.00%
0% - 50%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		$ 2,985	380
Loans Receivable, Loan to Value Ratio, Minimum	0.00%	0.00%
Loans Receivable, Loan to Value Ratio, Maximum	50.00%	50.00%
50% - 60%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		$ 1,436	1,173
Loans Receivable, Loan to Value Ratio, Minimum	50.00%	50.00%
Loans Receivable, Loan to Value Ratio, Maximum	60.00%	60.00%
60% - 70%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		$ 234	2,552
Loans Receivable, Loan to Value Ratio, Minimum	60.00%	60.00%
Loans Receivable, Loan to Value Ratio, Maximum	70.00%	70.00%
70% - 80%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		$ 15	509
Loans Receivable, Loan to Value Ratio, Minimum	70.00%	70.00%
Loans Receivable, Loan to Value Ratio, Maximum	80.00%	80.00%
>80% and above
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		$ 0	50
Loans Receivable, Loan to Value Ratio, Minimum	80.00%	80.00%
Year of Origination 2020
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		$ 282	0
Year of Origination 2020 | 0% - 50%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		98	0
Year of Origination 2020 | 50% - 60%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		156	0
Year of Origination 2020 | 60% - 70%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		28	0
Year of Origination 2020 | 70% - 80%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		0	0
Year of Origination 2020 | >80% and above
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		0	0
Year of Origination 2019
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		496	522
Year of Origination 2019 | 0% - 50%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		218	85
Year of Origination 2019 | 50% - 60%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		178	96
Year of Origination 2019 | 60% - 70%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		85	145
Year of Origination 2019 | 70% - 80%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		15	170
Year of Origination 2019 | >80% and above
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		0	26
Year of Origination 2018
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		290	349
Year of Origination 2018 | 0% - 50%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		114	4
Year of Origination 2018 | 50% - 60%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		102	88
Year of Origination 2018 | 60% - 70%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		74	110
Year of Origination 2018 | 70% - 80%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		0	133
Year of Origination 2018 | >80% and above
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		0	14
Year of Origination 2017
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		881	934
Year of Origination 2017 | 0% - 50%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		505	101
Year of Origination 2017 | 50% - 60%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		359	244
Year of Origination 2017 | 60% - 70%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		17	566
Year of Origination 2017 | 70% - 80%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		0	13
Year of Origination 2017 | >80% and above
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		0	10
Year of Origination 2016
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		684	697
Year of Origination 2016 | 0% - 50%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		394	46
Year of Origination 2016 | 50% - 60%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		284	150
Year of Origination 2016 | 60% - 70%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		6	470
Year of Origination 2016 | 70% - 80%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		0	31
Year of Origination 2016 | >80% and above
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		0	0
Year of Origination 2015
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		479	529
Year of Origination 2015 | 0% - 50%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		406	10
Year of Origination 2015 | 50% - 60%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		73	343
Year of Origination 2015 | 60% - 70%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		0	168
Year of Origination 2015 | 70% - 80%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		0	8
Year of Origination 2015 | >80% and above
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		0	0
Year of Origination 2014 and prior
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		1,558	1,633
Year of Origination 2014 and prior | 0% - 50%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		1,250	134
Year of Origination 2014 and prior | 50% - 60%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		284	252
Year of Origination 2014 and prior | 60% - 70%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		24	1,093
Year of Origination 2014 and prior | 70% - 80%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		0	154
Year of Origination 2014 and prior | >80% and above
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss		$ 0	$ 0