Commitments and Guarantees - Contractual Amounts of Credit-Related Off-Balance Sheet Financial Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Unfunded commitments to extend credit	$ 27,008	$ 26,993
Indemnified securities financing	379,459	360,452
Stable value protection	25,351	27,182
Standby letters of credit	$ 3,255	$ 3,459