Loans and Leases and the Allowance for Credit Losses - Interest Income Recognized on Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	$ 745,805	$ 757,701
Interest income recognized, Total	9,971	6,611
Interest income recognized, Cash basis	7,320	4,009
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	181,846	182,857
Interest income recognized, Total	3,147	975
Interest income recognized, Cash basis	3,147	975
Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	272,172	271,825
Interest income recognized, Total	783	478
Interest income recognized, Cash basis	783	478
Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	9,840	20,051
Interest income recognized, Total	1,682	429
Interest income recognized, Cash basis	1,682	429
Other Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	10,102	16,328
Interest income recognized, Total	6	847
Interest income recognized, Cash basis	6	847
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	121,209	103,875
Interest income recognized, Total	1,902	1,636
Interest income recognized, Cash basis	902	774
Residential Limited Documentation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	85,595	97,121
Interest income recognized, Total	1,728	1,500
Interest income recognized, Cash basis	696	384
Home Equity Lines and Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	48,797	45,542
Interest income recognized, Total	414	399
Interest income recognized, Cash basis	86	100
Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	13,125	16,504
Interest income recognized, Total	224	275
Interest income recognized, Cash basis	15	19
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	3,119	3,598
Interest income recognized, Total	85	72
Interest income recognized, Cash basis	$ 3	$ 3

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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://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 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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- 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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