Federal Funds Sold and Securities Financing Activities Securities Sold Under Agreements to Repurchase (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	$ 1,774	$ 1,503
US Treasury Securities [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	204	95
US Government Agencies Debt Securities [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	122	116
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	916	829
Commercial Paper [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	78	19
Corporate Debt Securities [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	454	444
Maturity Overnight [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	1,484	1,225
Maturity Overnight [Member] | US Treasury Securities [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	197	95
Maturity Overnight [Member] | US Government Agencies Debt Securities [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	112	101
Maturity Overnight [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	881	694
Maturity Overnight [Member] | Commercial Paper [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	78	19
Maturity Overnight [Member] | Corporate Debt Securities [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	216	316
Maturity up to 30 days [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	210	238
Maturity up to 30 days [Member] | US Treasury Securities [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	7	0
Maturity up to 30 days [Member] | US Government Agencies Debt Securities [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	10	15
Maturity up to 30 days [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	35	135
Maturity up to 30 days [Member] | Commercial Paper [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	0	0
Maturity up to 30 days [Member] | Corporate Debt Securities [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	158	88
Maturity 30 to 90 Days [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	80	40
Maturity 30 to 90 Days [Member] | US Treasury Securities [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	0	0
Maturity 30 to 90 Days [Member] | US Government Agencies Debt Securities [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	0	0
Maturity 30 to 90 Days [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	0	0
Maturity 30 to 90 Days [Member] | Commercial Paper [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	0	0
Maturity 30 to 90 Days [Member] | Corporate Debt Securities [Member]
securities sold under agreement to repurchase maturity [Line Items]
Securities Sold under Agreements to Repurchase	$ 80	$ 40