Derivative Instruments and Hedging Activities - Fair Value Asset/(Liability) of Credit Protection Sold (Details) - Credit Protection Sold - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Credit Derivatives
Fair Value Asset (Liability)	$ 2,335	$ 1,223
CDS
Credit Derivatives
Fair Value Asset (Liability)	2,338	1,227
Single-name CDS
Credit Derivatives
Fair Value Asset (Liability)	1,128	1,208
Single-name CDS | Investment grade
Credit Derivatives
Fair Value Asset (Liability)	1,447	1,230
Single-name CDS | Non-investment grade
Credit Derivatives
Fair Value Asset (Liability)	(319)	(22)
Index and basket CDS
Credit Derivatives
Fair Value Asset (Liability)	1,210	19
Index and basket CDS | Investment grade
Credit Derivatives
Fair Value Asset (Liability)	1,617	843
Index and basket CDS | Non-investment grade
Credit Derivatives
Fair Value Asset (Liability)	(407)	(824)
Other credit contracts
Credit Derivatives
Fair Value Asset (Liability)	$ (3)	$ (4)