Variable Interest Entities - Variable Interests Held by Us and Our Maximum Exposure to Loss Rising From Our Involvements in Those VIEs (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Variable Interest Held Classified as Assets	$ 2,331	$ 3,668
Variable Interests Held Classified as Liabilities	268	234
Total Assets in Unconsolidated VIEs	4,997	8,420
Maximum Exposure to Loss	3,541	6,676
Structured note vehicles [Member]
Variable Interest Entity [Line Items]
Variable Interest Held Classified as Assets	1,803	2,888
Variable Interests Held Classified as Liabilities	6	7
Total Assets in Unconsolidated VIEs	3,019	5,908
Maximum Exposure to Loss	3,013	5,896
Limited partnership investments [Member]
Variable Interest Entity [Line Items]
Variable Interest Held Classified as Assets	412	427
Variable Interests Held Classified as Liabilities	262	227
Total Assets in Unconsolidated VIEs	1,566	1,853
Maximum Exposure to Loss	412	427
Refinancing SPE [Member]
Variable Interest Entity [Line Items]
Variable Interest Held Classified as Assets	116	353
Variable Interests Held Classified as Liabilities	0	0
Total Assets in Unconsolidated VIEs	412	659
Maximum Exposure to Loss	$ 116	$ 353