Business Segments - Segment Operating Results (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jan. 01, 2021	Dec. 31, 2020
Product Liability Contingency [Line Items]
Operating expenses	$ 8,640	$ 10,414	$ 18,077	$ 16,872
Investment Banking and Global Markets [Member]
Product Liability Contingency [Line Items]
Operating expenses		$ 2,960		$ 3,140
Standardized Capital Rules [Member]
Product Liability Contingency [Line Items]
Standardized risk based ratios stress capital buffer	6.60%		6.60%		6.60%	6.60%