Restricted Cash, Other Restricted Assets and Intercompany Funds Transfers (Details) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2020	Jan. 01, 2021	Dec. 31, 2019
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash	$ 24.4		$ 46.5
Cash and securities pledged with clearing organizations for benefit of customers	37.2		24.7
Fair value of securities restricted in relation to customer activity	$ 1.3		8.8
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	$ 22.7		45.3
Cash and due from banks
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash	1.7		1.2
Cash reserves – Federal Reserve Banks
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash	0.0		26.6
Segregated for the benefit of securities and cleared derivative customers
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash	19.3		16.0
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	$ 5.1		$ 3.9
Bank and Bank Holding Company Subsidiaries | Subsequent Event
Disclosure of Restrictions on Dividends, Loans and Advances Disclosure [Abstract]
Aggregate dividends payable		$ 13.0