Fair Value Measurement - Transfers (Details) - Recurring - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative receivables | Equity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers from level 3 into level 2, assets		$ 2.1	$ 4.3
Transfers from level 2 into level 3, assets	$ 1.1	1.2
Trading loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers from level 3 into level 2, assets		2.8	2.7
Transfers from level 2 into level 3, assets	1.0		1.1
Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers from level 3 into level 2, assets		1.0
Corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers from level 3 into level 2, assets			2.0
Transfers from level 2 into level 3, assets		2.4
Margin loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers from level 3 into level 2, assets			2.6
Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers from level 3 into level 2, assets			2.3
Long-term debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers from level 3 into level 2, liabilities	1.4	3.1	1.3
Transfers from level 2 into level 3, liabilities			1.0
Derivative payables | Equity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers from level 3 into level 2, liabilities		2.1	4.4
Transfers from level 2 into level 3, liabilities	$ 1.0	$ 1.2
Other borrowed funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers from level 2 into level 3, liabilities			$ 1.1