Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Cash and investments segregated and on deposit for regulatory purposes, resale agreements	$ 14,904	$ 9,028
Amortized cost	$ 330,248	$ 61,155
Preferred stock, par value (USD per share)	$ 0.01	$ 0.01
Preferred stock, aggregate liquidation preference	$ 7,850	$ 2,850
Common stock, shares authorized (shares)	3,000,000,000	3,000,000,000
Common stock, par value (USD per share)	$ 0.01	$ 0.01
Common stock, shares issued (shares)	1,994,895,180	1,487,543,446
Treasury stock (shares)	193,577,648	201,818,100
Nonvoting Common Stock [Member]
Common stock, shares authorized (shares)	300,000,000	300,000,000
Common stock, par value (USD per share)	$ 0.01	$ 0.01
Common stock, shares issued (shares)	79,293,695	79,293,695