Pledged and Restricted Assets (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Financial Instruments Owned and Pledged as Collateral [Line Items]
Security owned and pledged as collateral, fair value	$ 51,200,000,000		$ 54,600,000,000
Securities eligible to be repledged or sold	328,100,000		524,100,000
Average deposits maintained to meet Federal Reserve Bank reserve requirements	0	$ 0
Collateral Requirements
Financial Instruments Owned and Pledged as Collateral [Line Items]
Security owned and pledged as collateral, fair value	$ 5,600,000,000		$ 5,600,000,000