Pledged and Restricted Assets (Narrative) (Details) - USD ($)	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Financial Instruments Owned and Pledged as Collateral [Line Items]
Average deposits maintained to meet Federal Reserve Bank reserve requirements	$ 0	$ 0
Collateral that may be repledged or sold
Financial Instruments Owned and Pledged as Collateral [Line Items]
Financial instruments owned at fair value	49,000,000,000.0		$ 54,600,000,000
Asset Pledged as Collateral with Right
Financial Instruments Owned and Pledged as Collateral [Line Items]
Financial instruments owned at fair value	1,144,700,000		524,100,000
Collateral Requirements | Collateral that may be repledged or sold
Financial Instruments Owned and Pledged as Collateral [Line Items]
Financial instruments owned at fair value	$ 8,100,000,000		$ 5,600,000,000