Loans - Average Recorded Investment and Interest Income on Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	$ 151,292	$ 118,697	$ 132,262	$ 128,485
Interest Income Recognized	1,035	1,093	2,944	3,220
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	70,135	31,499	49,037	28,008
Interest Income Recognized	300	293	896	727
Commercial real estate
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	60,761	64,752	60,554	75,685
Interest Income Recognized	503	550	1,350	1,765
Commercial real estate \| Commercial real estate
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	57,712	58,117	57,718	66,871
Interest Income Recognized	482	513	1,290	1,627
Commercial real estate \| Construction
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	3,049	6,635	2,836	8,814
Interest Income Recognized	21	37	60	138
Residential mortgage
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	15,630	20,193	17,851	22,232
Interest Income Recognized	183	225	575	660
Consumer loans
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	4,766	2,253	4,820	2,560
Interest Income Recognized	49	25	123	68
Consumer loans \| Home equity
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	4,766	2,253	4,820	2,560
Interest Income Recognized	$ 49	$ 25	$ 123	$ 68

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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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