Pledged and Restricted Assets (Type of Pledged Assets) (Details) - USD ($) $ in Billions	Jun. 30, 2021	Dec. 31, 2020
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total Pledged Assets	$ 51.2	$ 47.5
Obligations of States and Political Subdivisions
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total Pledged Assets	3.3	2.9
Government Sponsored Agency and Other Securities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total Pledged Assets	33.3	32.5
Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total Pledged Assets	$ 14.6	$ 12.1

Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

Name:	us-gaap_SecurityOwnedAndPledgedAsCollateralFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant