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, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Variable Interest Held Classified as Assets	$ 2,257	$ 2,331
Variable Interests Held Classified as Liabilities	229	268
Total Assets Held by Unconsolidated VIEs	4,611	4,997
Maximum Exposure to Loss	3,457	3,541
Structured note vehicles [Member]
Variable Interest Entity [Line Items]
Variable Interest Held Classified as Assets	1,803	1,803
Variable Interests Held Classified as Liabilities	20	6
Total Assets Held by Unconsolidated VIEs	3,033	3,019
Maximum Exposure to Loss	3,003	3,013
Limited partnership investments [Member]
Variable Interest Entity [Line Items]
Variable Interest Held Classified as Assets	454	412
Variable Interests Held Classified as Liabilities	209	262
Total Assets Held by Unconsolidated VIEs	1,578	1,566
Maximum Exposure to Loss	$ 454	412
Refinancing SPE [Member]
Variable Interest Entity [Line Items]
Variable Interest Held Classified as Assets		116
Variable Interests Held Classified as Liabilities		0
Total Assets Held by Unconsolidated VIEs		412
Maximum Exposure to Loss		$ 116