Commitments and Guarantees - Contractual Amounts of Credit-Related Off-Balance Sheet Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Unfunded credit facilities	$ 26,830	$ 26,488
Indemnified securities financing	399,064	381,817
Stable value protection	25,881	26,653
Standby letters of credit	$ 2,957	$ 3,158