Fair Value Option - Gains (Losses) Due to Changes in Instrument-Specific Credit Risk (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value disclosure
Cumulative pre-tax DVA gain (loss) recognized in AOCI	$ (3,357)	$ (1,998)
Loans and other debt | Trading revenues
Fair Value disclosure
Gains (losses) due to changes in instrument-specific credit risk	(116)	223	$ 165
Loans and other debt | OCI
Fair Value disclosure
Gains (losses) due to changes in instrument-specific credit risk	0	0	0
Lending commitments | Trading revenues
Fair Value disclosure
Gains (losses) due to changes in instrument-specific credit risk	(3)	(2)	(3)
Lending commitments | OCI
Fair Value disclosure
Gains (losses) due to changes in instrument-specific credit risk	0	0	0
Deposits | Trading revenues
Fair Value disclosure
Gains (losses) due to changes in instrument-specific credit risk	0	0	0
Deposits | OCI
Fair Value disclosure
Gains (losses) due to changes in instrument-specific credit risk	(19)	(30)	9
Borrowings | Trading revenues
Fair Value disclosure
Gains (losses) due to changes in instrument-specific credit risk	(26)	(11)	(24)
Borrowings | OCI
Fair Value disclosure
Gains (losses) due to changes in instrument-specific credit risk	$ (1,340)	$ (2,140)	1,962
Other | Trading revenues
Fair Value disclosure
Gains (losses) due to changes in instrument-specific credit risk			(32)
Other | OCI
Fair Value disclosure
Gains (losses) due to changes in instrument-specific credit risk			$ 32