Loans - Average Recorded Investment and Interest Income on Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	$ 163,903	$ 113,768
Interest Income Recognized	1,551	899
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	90,069	30,459
Interest Income Recognized	714	308
Commercial real estate
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	57,710	58,021
Interest Income Recognized	639	343
Commercial real estate \| Commercial real estate
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	55,493	55,325
Interest Income Recognized	616	324
Commercial real estate \| Construction
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	2,217	2,696
Interest Income Recognized	23	19
Residential mortgage
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	14,098	20,393
Interest Income Recognized	165	208
Consumer loans
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	2,026	4,895
Interest Income Recognized	33	40
Consumer loans \| Home equity
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	2,026	4,895
Interest Income Recognized	$ 33	$ 40

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- Definition

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

Reference 2: 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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- Definition

Amount of interest income recognized on a cash-basis method of accounting that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

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