Guarantee Arrangements and Pledged Assets and Repurchase Agreements - Offsetting of Resale and Repurchase Agreements and Securities Borrowing and Lending Agreements (Details) - USD ($) $ in Millions		Sep. 30, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Securities purchased under agreements to resell, Gross Amounts Recognized		$ 29,714	$ 19,167
Securities purchased under agreements to resell, Gross Amounts Offset in the Balance Sheet	[1]	4,135	1,329
Securities purchased under agreements to resell, Net amounts Prsented in the Balance Sheet		25,579	17,838
Securities purchased under agreements to resell, Gross Amounts Not Offset in the Balance Sheet, Financial Instruments	[2]	25,566	17,832
Securities purchased under agreements to resell, Gross Amounts Not Offset in the Balance Sheet, Cash Collateral Receive / Pledged		0	0
Securities purchased under agreements to resell, Net amount		13	6
Securities sold under repurchase agreements, Gross Amounts Recognized		6,320	2,401
Securities sold under repurchase agreements, Gross Amounts Offset in the Balance Sheet	[1]	4,135	1,329
Securities sold under repurchase agreements, Net Amounts Presented in the Balance Sheet		2,185	1,072
Securities sold under repurchase agreements, Gross Amounts Not Offset in the Balance sheet, Financial Instruments	[2]	2,148	1,068
Securities sold under repurchase agreements, Gross Amounts Not Offset in the Balance Sheet, Cash Collateral Received / Pledged		0	0
Securities sold under repurchase agreements, Net amount		$ 37	$ 4

[1] Represents recognized amount of resale and repurchase agreements with counterparties subject to legally enforceable netting agreements that meet the applicable netting criteria as permitted by generally accepted accounting principles.

[2] Represents securities received or pledged to cover financing transaction exposures.