Derivative Instruments and Hedging Activities - Fair Value Asset/(Liability) of Credit Protection Sold (Details) - Credit Protection Sold - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Credit Derivatives
Fair Value Asset (Liability)	$ 771	$ (1,398)
CDS
Credit Derivatives
Fair Value Asset (Liability)	789	(1,384)
Single-name CDS
Credit Derivatives
Fair Value Asset (Liability)	(296)	(285)
Single-name CDS | Investment grade
Credit Derivatives
Fair Value Asset (Liability)	663	118
Single-name CDS | Non-investment grade
Credit Derivatives
Fair Value Asset (Liability)	(959)	(403)
Index and basket CDS
Credit Derivatives
Fair Value Asset (Liability)	1,085	(1,099)
Index and basket CDS | Investment grade
Credit Derivatives
Fair Value Asset (Liability)	1,040	314
Index and basket CDS | Non-investment grade
Credit Derivatives
Fair Value Asset (Liability)	45	(1,413)
Other credit contracts
Credit Derivatives
Fair Value Asset (Liability)	$ (18)	$ (14)