Investments (Consolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Total Assets	$ 155	$ 59
Total Liabilities	6	12
Partnership [Member]
Variable Interest Entity [Line Items]
Total Assets	114	0
Total Liabilities	0	0
CSEs (assets (primarily loans) and liabilities (primarily debt))
Variable Interest Entity [Line Items]
Total Assets	7	9
Total Liabilities	6	12
Other
Variable Interest Entity [Line Items]
Total Assets	34	50
Total Liabilities	$ 0	$ 0