Interest-Bearing Deposits - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deposits [Abstract]
Interest-bearing demand deposit, money market	$ 1,100.0	$ 952.1
Certificates of deposit in denominations of $100 thousand or more	143.9	140.2
Interest expense related to certificates of deposit $100 thousand or greater	$ 3.3	$ 1.6	$ 0.5

Amount of interest-bearing domestic money market demand account 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=6876686&loc=d3e534808-122878

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