Securities Financing Activities (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Offsetting [Abstract]
Securities Purchased under Agreements to Resell	$ 976	$ 986
Securities Borrowed	369	431
Securities borrowed or purchased under resale agreements	1,345	1,417
Offsetting Liabilities [Line Items]
Short-term borrowings	5,700	18,218
Securities Sold under Agreements to Repurchase
Offsetting Liabilities [Line Items]
Short-term borrowings	1,123	1,969
Securities Sold under Agreements to Repurchase | U.S. Treasury
Offsetting Liabilities [Line Items]
Short-term borrowings	269	150
Securities Sold under Agreements to Repurchase | US Government-sponsored Enterprises Debt Securities
Offsetting Liabilities [Line Items]
Short-term borrowings	66	124
Securities Sold under Agreements to Repurchase | Residential Mortgage Backed Securities
Offsetting Liabilities [Line Items]
Short-term borrowings	437	1,069
Securities Sold under Agreements to Repurchase | Corporate Debt Securities
Offsetting Liabilities [Line Items]
Short-term borrowings	351	626
Securities Sold under Agreements to Repurchase | Maturity Overnight
Offsetting Liabilities [Line Items]
Short-term borrowings	828	1,440
Securities Sold under Agreements to Repurchase | Maturity Overnight | U.S. Treasury
Offsetting Liabilities [Line Items]
Short-term borrowings	240	115
Securities Sold under Agreements to Repurchase | Maturity Overnight | US Government-sponsored Enterprises Debt Securities
Offsetting Liabilities [Line Items]
Short-term borrowings	63	87
Securities Sold under Agreements to Repurchase | Maturity Overnight | Residential Mortgage Backed Securities
Offsetting Liabilities [Line Items]
Short-term borrowings	375	928
Securities Sold under Agreements to Repurchase | Maturity Overnight | Corporate Debt Securities
Offsetting Liabilities [Line Items]
Short-term borrowings	150	310
Securities Sold under Agreements to Repurchase | Maturity Less than 30 Days
Offsetting Liabilities [Line Items]
Short-term borrowings	295	429
Securities Sold under Agreements to Repurchase | Maturity Less than 30 Days | U.S. Treasury
Offsetting Liabilities [Line Items]
Short-term borrowings	29	35
Securities Sold under Agreements to Repurchase | Maturity Less than 30 Days | US Government-sponsored Enterprises Debt Securities
Offsetting Liabilities [Line Items]
Short-term borrowings	3	37
Securities Sold under Agreements to Repurchase | Maturity Less than 30 Days | Residential Mortgage Backed Securities
Offsetting Liabilities [Line Items]
Short-term borrowings	62	41
Securities Sold under Agreements to Repurchase | Maturity Less than 30 Days | Corporate Debt Securities
Offsetting Liabilities [Line Items]
Short-term borrowings	$ 201	316
Securities Sold under Agreements to Repurchase | Maturity 30 to 90 Days
Offsetting Liabilities [Line Items]
Short-term borrowings		100
Securities Sold under Agreements to Repurchase | Maturity 30 to 90 Days | U.S. Treasury
Offsetting Liabilities [Line Items]
Short-term borrowings		0
Securities Sold under Agreements to Repurchase | Maturity 30 to 90 Days | US Government-sponsored Enterprises Debt Securities
Offsetting Liabilities [Line Items]
Short-term borrowings		0
Securities Sold under Agreements to Repurchase | Maturity 30 to 90 Days | Residential Mortgage Backed Securities
Offsetting Liabilities [Line Items]
Short-term borrowings		100
Securities Sold under Agreements to Repurchase | Maturity 30 to 90 Days | Corporate Debt Securities
Offsetting Liabilities [Line Items]
Short-term borrowings		$ 0