Restricted Cash, Other Restricted Assets and Intercompany Funds Transfers (Details) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2018	Jan. 01, 2019	Dec. 31, 2017
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash	$ 40.8		$ 45.8
Cash and securities pledged with clearing organizations for benefit of customers	20.6		18.0
Fair value of securities restricted in relation to customer activity	$ 9.7		3.5
Disclosure of Restrictions on Dividends, Loans and Advances Disclosure [Abstract]
Percentage of total capital loans limited to	10.00%
Percentage of total capital (limited to) for aggregate covered transactions	20.00%
Deposits with banks
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash	$ 39.6		44.8
Cash and due from banks
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash	1.2		1.0
Cash reserves – Federal Reserve Banks
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash	22.1		25.7
Segregated for the benefit of securities and futures brokerage customers
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash	14.6		16.8
Cash reserves at non-U.S. central banks and held for other general purposes
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash	$ 4.1		$ 3.3
Bank and Bank Holding Company Subsidiaries | Subsequent Event
Disclosure of Restrictions on Dividends, Loans and Advances Disclosure [Abstract]
Aggregate dividends payable		$ 10.0