Investments (Consolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Total Assets	$ 3,615	$ 3,618
Total Liabilities	32	35
MRSC collateral financing arrangement
Variable Interest Entity [Line Items]
Total Assets	3,423	3,422
Total Liabilities	0	0
CSEs (assets (primarily loans) and liabilities (primarily debt))
Variable Interest Entity [Line Items]
Total Assets	142	146
Total Liabilities	32	35
Other
Variable Interest Entity [Line Items]
Total Assets	50	50
Total Liabilities	$ 0	$ 0