Derivative Instruments and Hedging Activities - Offsetting Assets (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Derivative assets
Derivative assets, gross amount	$ 4,904	$ 3,415
Derivative assets, offsetting financial instruments	(434)	(383)
Derivative assets, offsetting cash collateral	(541)	(765)
Total derivative assets	3,929	2,267
Derivative assets, securities not netted	0	0
Net Exposure	3,929	2,267
Derivative, collateral, obligation to return cash	653	862
Derivative, collateral, obligation to return securities	1	1
Derivative, collateral, right to reclaim cash	$ 2,500	$ 1,500