Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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Allowance for Loan Losses - Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of the period				$ 14,837				$ 14,534	$ 14,837	$ 14,534	$ 16,501
Total loans charged-off									2,253	2,660	6,099
Total loan recoveries									1,340	1,121	970
Net loans charged-off									913	1,539	5,129
Total provision charged to operating expense	$ 1,100	$ 710	$ 330	$ 330	$ 623	$ 455	$ 232	$ 532	2,470	1,842	3,162
Balance at the end of the period	$ 16,394				$ 14,837				16,394	14,837	14,534
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off									377	758	3,437
Total loan recoveries									268	210	192
Total provision charged to operating expense									2,164	(68)	2,531
Commercial [Member] \| Owner Occupied Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off									68	181	2,208
Total loan recoveries									9	31	104
Commercial [Member] \| Non Owner Occupied Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off									20	471	556
Total loan recoveries									32	55	1
Commercial [Member] \| Residential Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loan recoveries									8	8
Commercial [Member] \| Development & Spec Land Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off									1
Total loan recoveries											35
Commercial [Member] \| Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off									288	106	673
Total loan recoveries									219	116	52
Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off									89	213	288
Total loan recoveries									44	97	69
Total provision charged to operating expense									(81)	(23)	62
Real Estate [Member] \| Residential Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off									89	213	288
Total loan recoveries									44	97	69
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off									1,787	1,689	2,374
Total loan recoveries									1,028	814	709
Total provision charged to operating expense									387	1,933	569
Consumer [Member] \| Direct Installment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off									389	329	367
Total loan recoveries									531	81	106
Consumer [Member] \| Indirect Installment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off									1,193	1,051	1,081
Total loan recoveries									497	529	489
Consumer [Member] \| Home Equity Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off									$ 205	309	926
Total loan recoveries										$ 204	$ 114