Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Name:	us-gaap_GoodwillImpairmentLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Goodwill and Core Deposit Intangibles - Goodwill Narrative (Details) - USD ($)	Jul. 01, 2017	Jul. 01, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill			$ 546,700,000	$ 444,700,000	$ 212,800,000
Impairment of goodwill	$ 0	$ 0