Investments (excluding Consolidated Investment Entities) - Loans by Loan to Value (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
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%	100.00%
Total Commercial mortgage loans	$ 8,689	$ 8,006
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%
Commercial mortgage loans	$ 849	$ 950
Greater than 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%
Commercial mortgage loans	$ 2,125	$ 1,976
Greater than 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%
Commercial mortgage loans	$ 5,144	$ 4,544
Greater than 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%
Commercial mortgage loans	$ 551	$ 523
Greater than 80% and above
Schedule of Loans by Loan to Value Ratio [Line Items]
Loan to Value Ratio, minimum	80.00%	80.00%
Commercial mortgage loans	$ 20	$ 13
Less than 80%
Schedule of Loans by Loan to Value Ratio [Line Items]
Loan to Value Ratio, maximum	80.00%	80.00%