Investments - Loans by Loan to Value Ratio and Debt Service Coverage Ratio (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Schedule of Loans by Loan to Value Ratio [Line Items]
Benchmark loan to value ratio, greater than indicates unpaid loan amount exceeds underlying collateral	100.00%
Benchmark debt service coverage ratio, less than indicates property's operations income is less than debt payments	100.00%
Commercial mortgage loans	$ 4,664	$ 4,919
Loans, Loan-to-value ratio, Percent of total Loans	100.00%	100.00%
1.5x
Schedule of Loans by Loan to Value Ratio [Line Items]
Commercial mortgage loans	$ 3,535	$ 3,718
Loans Receivable, Debt Service Coverage Ratio, Minimum	150.00%	150.00%
1.25x - 1.5x
Schedule of Loans by Loan to Value Ratio [Line Items]
Commercial mortgage loans	$ 587	$ 484
Loans Receivable, Debt Service Coverage Ratio, Minimum	125.00%	125.00%
Loans Receivable, Debt Service Coverage Ratio, Maximum	150.00%	150.00%
1.0x - 1.25x
Schedule of Loans by Loan to Value Ratio [Line Items]
Commercial mortgage loans	$ 346	$ 613
Loans Receivable, Debt Service Coverage Ratio, Minimum	100.00%	100.00%
Loans Receivable, Debt Service Coverage Ratio, Maximum	125.00%	125.00%
1.0x
Schedule of Loans by Loan to Value Ratio [Line Items]
Commercial mortgage loans	$ 196	$ 53
Loans Receivable, Debt Service Coverage Ratio, Minimum	0.00%	0.00%
Loans Receivable, Debt Service Coverage Ratio, Maximum	100.00%	100.00%
Commercial Loan
Schedule of Loans by Loan to Value Ratio [Line Items]
Commercial mortgage loans	$ 0	$ 51
0% - 50%
Schedule of Loans by Loan to Value Ratio [Line Items]
Loan to Value Ratio, minimum	0.00%	0.00%
Loan to Value Ratio, maximum	50.00%	50.00%
50% - 60%
Schedule of Loans by Loan to Value Ratio [Line Items]
Loan to Value Ratio, minimum	50.00%	50.00%
Loan to Value Ratio, maximum	60.00%	60.00%
60% - 70%
Schedule of Loans by Loan to Value Ratio [Line Items]
Loan to Value Ratio, minimum	60.00%	60.00%
Loan to Value Ratio, maximum	70.00%	70.00%
70% - 80%
Schedule of Loans by Loan to Value Ratio [Line Items]
Loan to Value Ratio, minimum	70.00%	70.00%
Loan to Value Ratio, maximum	80.00%	80.00%