Allowance for Loan Losses - Narrative (Details) - Loans - Bank Shares, Inc - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Remaining fair value adjustment for loans acquired	$ 13.4	$ 19.4
Percentage of fair value adjustment for loans acquired	2.00%	2.20%

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.

No definition available.

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