Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Cash and investments segregated and on deposit for regulatory purposes, resale agreements	$ 4,434	$ 6,596
Held to maturity securities	$ 123,463	$ 120,373
Preferred stock, par value (USD per share)	$ 0.01	$ 0.01
Preferred stock, aggregate liquidation preference	$ 2,850	$ 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)	1,487,543,446	1,487,543,446
Treasury stock (shares)	139,326,005	142,210,890