Securities Financing Activities (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Offsetting [Abstract]
Securities Purchased under Agreements to Resell	$ 1,295	$ 986
Securities Borrowed	501	431
Securities borrowed or purchased under resale agreements	1,796	1,417
Offsetting Liabilities [Line Items]
Short-term borrowings	12,696	18,218
Securities Sold under Agreements to Repurchase
Offsetting Liabilities [Line Items]
Short-term borrowings	1,529	1,969
Securities Sold under Agreements to Repurchase | U.S. Treasury
Offsetting Liabilities [Line Items]
Short-term borrowings	230	150
Securities Sold under Agreements to Repurchase | US Government-sponsored Enterprises Debt Securities [Member]
Offsetting Liabilities [Line Items]
Short-term borrowings	175	124
Securities Sold under Agreements to Repurchase | Residential Mortgage Backed Securities
Offsetting Liabilities [Line Items]
Short-term borrowings	720	1,069
Securities Sold under Agreements to Repurchase | Corporate Debt Securities
Offsetting Liabilities [Line Items]
Short-term borrowings	404	626
Securities Sold under Agreements to Repurchase | Maturity Overnight
Offsetting Liabilities [Line Items]
Short-term borrowings	1,168	1,440
Securities Sold under Agreements to Repurchase | Maturity Overnight | U.S. Treasury
Offsetting Liabilities [Line Items]
Short-term borrowings	230	115
Securities Sold under Agreements to Repurchase | Maturity Overnight | US Government-sponsored Enterprises Debt Securities [Member]
Offsetting Liabilities [Line Items]
Short-term borrowings	171	87
Securities Sold under Agreements to Repurchase | Maturity Overnight | Residential Mortgage Backed Securities
Offsetting Liabilities [Line Items]
Short-term borrowings	575	928
Securities Sold under Agreements to Repurchase | Maturity Overnight | Corporate Debt Securities
Offsetting Liabilities [Line Items]
Short-term borrowings	192	310
Securities Sold under Agreements to Repurchase | Maturity Less than 30 Days
Offsetting Liabilities [Line Items]
Short-term borrowings	361	429
Securities Sold under Agreements to Repurchase | Maturity Less than 30 Days | U.S. Treasury
Offsetting Liabilities [Line Items]
Short-term borrowings	0	35
Securities Sold under Agreements to Repurchase | Maturity Less than 30 Days | US Government-sponsored Enterprises Debt Securities [Member]
Offsetting Liabilities [Line Items]
Short-term borrowings	4	37
Securities Sold under Agreements to Repurchase | Maturity Less than 30 Days | Residential Mortgage Backed Securities
Offsetting Liabilities [Line Items]
Short-term borrowings	145	41
Securities Sold under Agreements to Repurchase | Maturity Less than 30 Days | Corporate Debt Securities
Offsetting Liabilities [Line Items]
Short-term borrowings	$ 212	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 [Member]
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