Allowance for Loan Losses - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Modifications [Line Items]
Provision for Loan, Lease, and Other Losses	$ 5,648	$ 2,411	$ 2,644
Allowance for Loan and Lease Losses, Write-offs	4,102	1,144	3,380
Allowance for Loan and Lease Loss, Recovery of Bad Debts	2,495	3,236	3,012
Purchased Unimpaired Loans [Member]
Financing Receivable, Modifications [Line Items]
Provision for Loan, Lease, and Other Losses	(400)		(1,300)
Allowance for Loan and Lease Losses, Write-offs			$ 1,200
Allowance for Loan and Lease Loss, Recovery of Bad Debts	1,000
Loans [Member] | Bank shares, Inc [Member]
Financing Receivable, Modifications [Line Items]
Assets, Fair Value Adjustment	$ 17,500	$ 13,700
Fair value adjustment Percent	2.00%	3.11%