Deposits - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Banking and Thrift [Abstract]
Weighted-average interest rate on certificates of deposit (as a percent)	2.11%	1.87%
Time Deposits, at or Above FDIC Insurance Limit	$ 113.9	$ 85.3
Brokered deposits	$ 731.8	$ 786.1

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=6876686&loc=d3e534808-122878

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