Investment Securities (Schedule of Carrying Value of Investment Securities) (Parenthetical) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Investments Debt And Equity Securities [Abstract]
Restricted Stock of FRB and FHLB	$ 240.1	$ 187.9
Non-marketable investments without readily determinable fair values	$ 33.8	$ 29.9

Amount of investment in equity security without readily determinable fair value.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117539-209714

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant