Number of banking offices.

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Number of shares of equity interests issued or issuable to acquire entity.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Mergers and acquisitions - Clayton Bank and Trust and American City Bank Narrative (Details)		1 Months Ended	12 Months Ended
	Feb. 08, 2017 USD ($) shares	Jul. 31, 2017 USD ($) bank_location	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Goodwill			$ 137,190,000	$ 137,190,000	$ 46,867,000
Merger and conversion			1,594,000	19,034,000	$ 3,268,000
Business combination, deferred taxes			19,726,000	17,768,000
Clayton Bank and Trust and American City Bank
Business Acquisition [Line Items]
Acquisition purchase price	$ 236,484,000	$ 236,484,000
Business acquisition, shares issued (in shares) \| shares	1,521,200
Cash purchase price	$ 184,200,000	$ 184,200,000
Number of banking offices \| bank_location		18
Goodwill		$ 90,323,000
Merger and conversion			$ 1,193,000	$ 19,034,000
Business combination, deferred taxes		$ 0