Non-performing Loans and Impaired Loans - Commercial Loans Individually Evaluated for Impairment by Class of Loan (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance total	$ 6,777	$ 1,379
Total ending loans balance	6,824	1,379
Allowance For Loan Loss Allocated	184
Average Balance in Impaired Loans total	7,987	2,002
Cash/Accrual Interest Income Recognized, Total	42
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance With no recorded allowance	5,884	1,379
Recorded Investment With no recorded allowance	5,931	1,379
Allowance For Loan Loss Allocated With no recorded allowance	0	0
Average Balance in Impaired Loans With no recorded allowance	7,087	2,002
Cash/Accrual Interest Income Recognized, With no recorded allowance	42
Unpaid Principal Balance With an allowance recorded	893
Recorded Investment With an allowance recorded	893
Allowance For Loan Loss Allocated	184
Average Balance in Impaired Loans With an allowance recorded	900
Cash/Accrual Interest Income Recognized, With an allowance recorded	0	0
Commercial [Member] \| Owner Occupied Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance With no recorded allowance	4,038	759
Recorded Investment With no recorded allowance	4,063	759
Allowance For Loan Loss Allocated With no recorded allowance	0	0
Average Balance in Impaired Loans With no recorded allowance	4,590	1,021
Cash/Accrual Interest Income Recognized, With no recorded allowance	37
Unpaid Principal Balance With an allowance recorded	893
Recorded Investment With an allowance recorded	893
Allowance For Loan Loss Allocated	184
Average Balance in Impaired Loans With an allowance recorded	900
Cash/Accrual Interest Income Recognized, With an allowance recorded	0	0
Commercial [Member] \| Non Owner Occupied Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance With no recorded allowance	1,033	387
Recorded Investment With no recorded allowance	1,049	387
Allowance For Loan Loss Allocated With no recorded allowance	0	0
Average Balance in Impaired Loans With no recorded allowance	975	393
Cash/Accrual Interest Income Recognized, With no recorded allowance	5
Cash/Accrual Interest Income Recognized, With an allowance recorded	0	0
Commercial [Member] \| Residential Spec Homes [Member]
Financing Receivable, Impaired [Line Items]
Allowance For Loan Loss Allocated With no recorded allowance	0	0
Cash/Accrual Interest Income Recognized, With an allowance recorded	0	0
Commercial [Member] \| Development & Spec Land [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance With no recorded allowance	76	112
Recorded Investment With no recorded allowance	74	112
Allowance For Loan Loss Allocated With no recorded allowance	0	0
Average Balance in Impaired Loans With no recorded allowance	75	238
Cash/Accrual Interest Income Recognized, With an allowance recorded	0	0
Commercial [Member] \| Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance With no recorded allowance	737	121
Recorded Investment With no recorded allowance	745	121
Allowance For Loan Loss Allocated With no recorded allowance	0	0
Average Balance in Impaired Loans With no recorded allowance	1,447	350
Cash/Accrual Interest Income Recognized, With an allowance recorded	$ 0	$ 0

Impaired financing receivable interest income accrual method and cash basis method.

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- Definition

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Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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-Section 50
-Paragraph 14A
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-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953550-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

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-Publisher FASB
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-Section 50
-Paragraph 15
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-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

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