Commitments and Guarantees - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Unfunded commitments to extend credit, short term	76.00%
Term of unfunded commitment	1 year
Cash collateral provided for securities lending		$ 19,400
Accrued expenses and other liabilities
Loss Contingencies [Line Items]
Cash collateral received in connection to securities finance activities	$ 15,617	$ 3,850