Customer Contract Revenue Recognition (Change in Revenue) (Details) - Revenue from Contracts with Customers $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Change in Revenue as a Result of Application of the New Revenue Recognition Standard
Change in revenues	$ 83
Increase to net revenues and noncompensation expenses	79
Investment Banking
Change in Revenue as a Result of Application of the New Revenue Recognition Standard
Change in revenues	60
Commissions and Fees
Change in Revenue as a Result of Application of the New Revenue Recognition Standard
Change in revenues	2
Asset Management
Change in Revenue as a Result of Application of the New Revenue Recognition Standard
Change in revenues	9
Ohter Customer Contract Revenues
Change in Revenue as a Result of Application of the New Revenue Recognition Standard
Change in revenues	12
I/E
Change in Revenue as a Result of Application of the New Revenue Recognition Standard
Increase to net revenues and noncompensation expenses	(16)
Institutional Securities
Change in Revenue as a Result of Application of the New Revenue Recognition Standard
Increase to net revenues and noncompensation expenses	72
Institutional Securities | Advisory
Change in Revenue as a Result of Application of the New Revenue Recognition Standard
Change in revenues	15
Institutional Securities | Underwriting
Change in Revenue as a Result of Application of the New Revenue Recognition Standard
Change in revenues	45
Investment Management
Change in Revenue as a Result of Application of the New Revenue Recognition Standard
Increase to net revenues and noncompensation expenses	$ 23