Investments - Loans by Loan to Value (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 4,774	$ 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	$ 2,941	$ 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	$ 1,566	$ 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	$ 252	$ 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	$ 195	$ 0
Year of Origination 2020 | 0% - 50%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss	41	0
Year of Origination 2020 | 50% - 60%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss	126	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	510	522
Year of Origination 2019 | 0% - 50%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss	263	85
Year of Origination 2019 | 50% - 60%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss	152	96
Year of Origination 2019 | 60% - 70%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss	80	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	315	349
Year of Origination 2018 | 0% - 50%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss	116	4
Year of Origination 2018 | 50% - 60%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss	109	88
Year of Origination 2018 | 60% - 70%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss	90	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	926	934
Year of Origination 2017 | 0% - 50%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss	547	101
Year of Origination 2017 | 50% - 60%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss	362	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	693	697
Year of Origination 2016 | 0% - 50%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss	400	46
Year of Origination 2016 | 50% - 60%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss	280	150
Year of Origination 2016 | 60% - 70%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss	13	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	526	529
Year of Origination 2015 | 0% - 50%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss	381	10
Year of Origination 2015 | 50% - 60%
Schedule of Loans by Loan to Value Ratio [Line Items]
Financing Receivable, before Allowance for Credit Loss	145	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	1,609	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	1,193	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	392	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