Loans - Average Recorded Investment and Interest Income Recognized on Impaired Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	$ 125,941	$ 150,291	$ 155,333
Interest Income Recognized	4,291	4,646	5,010
Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	21,340	24,435	26,863
Interest Income Recognized	874	728	812
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	65,423	93,553	95,771
Interest Income Recognized	2,304	2,914	3,035
Commercial real estate \| Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	59,633	77,154	74,256
Interest Income Recognized	2,122	2,380	2,488
Commercial real estate \| Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	5,790	16,399	21,515
Interest Income Recognized	182	534	547
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	36,552	28,451	30,485
Interest Income Recognized	1,045	893	1,114
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	2,626	3,852	2,214
Interest Income Recognized	68	111	49
Consumer \| Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	2,626	3,852	2,214
Interest Income Recognized	$ 68	$ 111	$ 49

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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=66008989&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=66008989&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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