Investments (Consolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Total Assets	$ 3,618	$ 6,101
Total Liabilities	35	2,141
MRSC (collateral financing arrangement (primarily securities))
Variable Interest Entity [Line Items]
Total Assets	3,422	3,374
Total Liabilities	0	0
Operating joint venture
Variable Interest Entity [Line Items]
Total Assets	0	2,465
Total Liabilities	0	2,079
CSEs (assets (primarily loans) and liabilities (primarily debt))
Variable Interest Entity [Line Items]
Total Assets	146	186
Total Liabilities	35	62
Other
Variable Interest Entity [Line Items]
Total Assets	50	76
Total Liabilities	$ 0	$ 0