Commitments, Leases, Guarantees and Contingencies - Balance Sheet Amounts Related to Leases (Details) $ in Millions	Sep. 30, 2019 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Other assets—ROU assets	$ 3,825
Lease liabilities	$ 4,535
Weighted average:
Remaining lease term, in years	9 years 7 months 6 days
Discount rate (as a percent)	3.70%