Premises and Equipment, Net - Additional Information (Details) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($) Branch	Dec. 31, 2017 USD ($) Branch	Dec. 31, 2016 USD ($)
Property Plant And Equipment [Abstract]
Number of branches held for sale \| Branch	3	3
Property valuation adjustments	$ 173	$ 338	$ 750
Premises and Equipment, Net, by Type [Abstract]
Depreciation and amortization of premises and equipment	$ 14,300	$ 14,300	$ 13,200

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=109226348&loc=d3e2420-110228

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