Deposits - Certificates of deposits and Scheduled maturities of time deposits (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Deposits
Aggregate amounts of certificates of deposits in denominations of $250,000 or more	$ 658.2	$ 814.2
Traditional, out-of-market brokered deposits	$ 325.1	$ 600.0

Amount of interest-bearing domestic third-party deposits placed by or through the assistance of a deposit broker, also known as brokered deposit liabilities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.12)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Name:	us-gaap_InterestBearingDomesticDepositBrokered
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant