Loans and Leases and Other Real Estate - Allowance for Loan and Lease Losses by Portfolio Segment and Related Recorded Investment in Loans and Leases (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 35,455	$ 31,245
Charge-offs	(3,347)	(3,446)
Recoveries	1,167	1,566
Provision	4,413	6,090	$ 4,223
Ending balance: Individually evaluated for impairment	338	505
Ending balance	37,688	35,455	31,245
Ending balance: Collectively evaluated for impairment	37,350	34,950
Loans and Leases
Total Loans and Leases	4,460,447	4,156,680
Loans and Leases
Loans and Leases
Ending balance: Individually evaluated for impairment	19,702	22,591
Ending balance: Collectively evaluated for impairment	4,440,093	4,133,379
Total Loans and Leases	4,460,447	4,156,680
Loans and Leases \| Loans Acquired with Deteriorated Credit Quality
Loans and Leases
Ending balance: Loans acquired with deteriorated credit quality	652	710
Commercial, secured by real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	25,704	21,223
Charge-offs	(421)	(762)
Recoveries	468	396
Provision	2,130	4,847
Ending balance: Individually evaluated for impairment	307	454	392
Ending balance	27,881	25,704	21,223
Ending balance: Collectively evaluated for impairment	27,574	25,250
Loans and Leases
Total Loans and Leases	3,057,779	2,831,184
Commercial, secured by real estate \| Loans and Leases
Loans and Leases
Ending balance: Individually evaluated for impairment	16,554	17,536
Ending balance: Collectively evaluated for impairment	3,040,573	2,812,941
Total Loans and Leases	3,057,779	2,831,184
Commercial, secured by real estate \| Loans and Leases \| Loans Acquired with Deteriorated Credit Quality
Loans and Leases
Ending balance: Loans acquired with deteriorated credit quality	652	707
Commercial, industrial and other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,313	1,723
Charge-offs	(1,452)	(477)
Recoveries	317	172
Provision	564	895
Ending balance: Individually evaluated for impairment	7	9	12
Ending balance	1,742	2,313	1,723
Ending balance: Collectively evaluated for impairment	1,735	2,304
Loans and Leases
Total Loans and Leases	336,735	340,400
Commercial, industrial and other \| Loans and Leases
Loans and Leases
Ending balance: Individually evaluated for impairment	1,360	782
Ending balance: Collectively evaluated for impairment	335,375	339,618
Total Loans and Leases	336,735	340,400
Commercial, industrial and other \| Loans and Leases \| Loans Acquired with Deteriorated Credit Quality
Loans and Leases
Ending balance: Loans acquired with deteriorated credit quality	0	0
Leases
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	630	548
Charge-offs	(507)	(305)
Recoveries	23	59
Provision	841	328
Ending balance: Individually evaluated for impairment	14	30	0
Ending balance	987	630	548
Ending balance: Collectively evaluated for impairment	973	600
Loans and Leases
Total Loans and Leases	87,925	75,039
Leases \| Loans and Leases
Loans and Leases
Ending balance: Individually evaluated for impairment	331	65
Ending balance: Collectively evaluated for impairment	87,594	74,974
Total Loans and Leases	87,925	75,039
Leases \| Loans and Leases \| Loans Acquired with Deteriorated Credit Quality
Loans and Leases
Ending balance: Loans acquired with deteriorated credit quality	0	0
Real estate - residential mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,557	1,964
Charge-offs	(131)	(441)
Recoveries	10	5
Provision	130	29
Ending balance: Individually evaluated for impairment	4	4	31
Ending balance	1,566	1,557	1,964
Ending balance: Collectively evaluated for impairment	1,562	1,553
Loans and Leases
Total Loans and Leases	329,854	322,880
Real estate - residential mortgage \| Loans and Leases
Loans and Leases
Ending balance: Individually evaluated for impairment	730	1,744
Ending balance: Collectively evaluated for impairment	329,124	321,136
Total Loans and Leases	329,854	322,880
Real estate - residential mortgage \| Loans and Leases \| Loans Acquired with Deteriorated Credit Quality
Loans and Leases
Ending balance: Loans acquired with deteriorated credit quality	0	0
Real estate - construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,731	2,352
Charge-offs	(248)	(609)
Recoveries	17	31
Provision	515	957
Ending balance: Individually evaluated for impairment	0	0	0
Ending balance	3,015	2,731	2,352
Ending balance: Collectively evaluated for impairment	3,015	2,731
Loans and Leases
Total Loans and Leases	319,545	264,908
Real estate - construction \| Loans and Leases
Loans and Leases
Ending balance: Individually evaluated for impairment	0	1,471
Ending balance: Collectively evaluated for impairment	319,545	263,437
Total Loans and Leases	319,545	264,908
Real estate - construction \| Loans and Leases \| Loans Acquired with Deteriorated Credit Quality
Loans and Leases
Ending balance: Loans acquired with deteriorated credit quality	0	0
Home equity and consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,520	3,435
Charge-offs	(588)	(852)
Recoveries	332	903
Provision	233	(966)
Ending balance: Individually evaluated for impairment	6	8	94
Ending balance	2,497	2,520	$ 3,435
Ending balance: Collectively evaluated for impairment	2,491	2,512
Loans and Leases
Total Loans and Leases	328,609	322,269
Home equity and consumer \| Loans and Leases
Loans and Leases
Ending balance: Individually evaluated for impairment	727	993
Ending balance: Collectively evaluated for impairment	327,882	321,273
Total Loans and Leases	328,609	322,269
Home equity and consumer \| Loans and Leases \| Loans Acquired with Deteriorated Credit Quality
Loans and Leases
Ending balance: Loans acquired with deteriorated credit quality	$ 0	$ 3

Provision recovery for loan and lease losses.

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- Definition

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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The balance of financing receivables that were individually evaluated for impairment.

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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 6.L.1)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544

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- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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- Definition

Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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