Long-Term Borrowings and Other Secured Financings (Other Narratives) (Details) - USD ($) $ in Billions	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Long-term Borrowings
Notes issued, principal amount	$ 30.2	$ 26.5
Notes matured or retired	$ 17.6	$ 24.7
Weighted average maturity of long-term borrowings	5 years 11 months		5 years 11 months