Investments (Consolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Total Assets	$ 202	$ 148
Total Liabilities	6	9
Partnership [Member]
Variable Interest Entity [Line Items]
Total Assets	102	116
Total Liabilities	0	3
CSEs (assets (primarily loans) and liabilities (primarily debt))
Variable Interest Entity [Line Items]
Total Assets	79	0
Total Liabilities	1	0
Other
Variable Interest Entity [Line Items]
Total Assets	21	32
Total Liabilities	$ 5	$ 6