Loans and the Allowance for Credit Losses - Recorded Investment in Non-Accrual Loans and TDRs (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Non-accrual loans	$ 31,981	$ 36,825
TDRs	8,974	9,436
Accruing TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	6,460	6,571
Non-Accrual TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	2,514	2,865
Commercial Real Estate - Land and Construction [Member]
Financing Receivable, Impaired [Line Items]
Non-accrual loans		239
TDRs		3
Commercial Real Estate - Land and Construction [Member] \| Non-Accrual TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs		3
Commercial Real Estate - Improved Property [Member]
Financing Receivable, Impaired [Line Items]
Non-accrual loans	9,479	13,318
TDRs	2,027	2,078
Commercial Real Estate - Improved Property [Member] \| Accruing TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	1,410	1,650
Commercial Real Estate - Improved Property [Member] \| Non-Accrual TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	617	428
Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
Non-accrual loans	3,191	2,958
TDRs	217	225
Commercial and Industrial [Member] \| Accruing TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	126	128
Commercial and Industrial [Member] \| Non-Accrual TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	91	97
Home Equity [Member]
Financing Receivable, Impaired [Line Items]
Non-accrual loans	4,726	4,762
TDRs	641	744
Home Equity [Member] \| Accruing TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	417	407
Home Equity [Member] \| Non-Accrual TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	224	337
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Non-accrual loans	9,479	13,557
TDRs	2,027	2,081
Commercial Real Estate [Member] \| Accruing TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	1,410	1,650
Commercial Real Estate [Member] \| Non-Accrual TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	617	431
Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Non-accrual loans	13,951	14,661
TDRs	5,944	6,201
Residential Real Estate [Member] \| Accruing TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	4,428	4,321
Residential Real Estate [Member] \| Non-Accrual TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	1,516	1,880
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Non-accrual loans	634	887
TDRs	145	185
Consumer [Member] \| Accruing TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	79	65
Consumer [Member] \| Non-Accrual TDRs [Member]
Financing Receivable, Impaired [Line Items]
TDRs	$ 66	$ 120

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No definition available.

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- Definition

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18845-111554

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- Definition

Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5111-111524

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