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	Jun. 30, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Total Assets Held by Unconsolidated VIEs	$ 3,563	$ 4,611
Variable Interest Held Classified as Assets	1,052	2,257
Variable Interests Held Classified as Liabilities	271	229
Maximum Exposure to Loss	2,085	3,457
Structured note vehicles [Member]
Variable Interest Entity [Line Items]
Total Assets Held by Unconsolidated VIEs	1,526	3,033
Variable Interest Held Classified as Assets	510	1,803
Variable Interests Held Classified as Liabilities	11	20
Maximum Exposure to Loss	1,515	3,003
Limited partnership investments [Member]
Variable Interest Entity [Line Items]
Total Assets Held by Unconsolidated VIEs	2,037	1,578
Variable Interest Held Classified as Assets	542	454
Variable Interests Held Classified as Liabilities	260	209
Maximum Exposure to Loss	$ 570	$ 454