Loans - Average Recorded Investment and Interest Income Recognized on Impaired Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	$ 170,675	$ 158,777	$ 125,941
Interest Income Recognized	4,707	4,373	4,291
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	108,071	80,974	36,552
Interest Income Recognized	1,822	1,459	1,045
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	46,355	58,057	65,423
Interest Income Recognized	2,358	1,994	2,304
Commercial real estate \| Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	44,838	54,799	59,633
Interest Income Recognized	2,289	1,908	2,122
Commercial real estate \| Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	1,517	3,258	5,790
Interest Income Recognized	69	86	182
Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	15,384	15,451	21,340
Interest Income Recognized	506	760	874
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	865	4,295	2,626
Interest Income Recognized	21	160	68
Consumer \| Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	865	4,295	2,626
Interest Income Recognized	$ 21	$ 160	$ 68

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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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://fasb.org/us-gaap/role/ref/legacyRef
-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://fasb.org/us-gaap/role/ref/legacyRef
-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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