Loans and Other Real Estate - Allowance for Loan and Lease Losses by Portfolio Segment (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 4,924,671	$ 4,460,447
Ending Balance: Individually evaluated for impairment, related allowance	259	338
Ending Balance	37,979	37,688	$ 35,644	$ 35,455
Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Ending Balance: Individually evaluated for impairment	20,236	19,702
Ending Balance: Collectively evaluated for impairment	4,890,055	4,440,093
Ending Balance: Loans acquired with deteriorated credit quality	14,380	652
Total Loans	4,924,671	4,460,447
Ending Balance: Individually evaluated for impairment, related allowance	259	338
Ending Balance: Collectively evaluated for impairment, related allowance	37,720	37,350
Ending Balance	37,979	37,688
Commercial, secured by real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	3,436,550	3,057,779
Ending Balance: Individually evaluated for impairment, related allowance	229	307
Ending Balance	27,515	27,881	25,817	25,704
Commercial, secured by real estate \| Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Ending Balance: Individually evaluated for impairment	15,985	16,554
Ending Balance: Collectively evaluated for impairment	3,413,062	3,040,573
Ending Balance: Loans acquired with deteriorated credit quality	7,503	652
Total Loans	3,436,550	3,057,779
Ending Balance: Individually evaluated for impairment, related allowance	229	307
Ending Balance: Collectively evaluated for impairment, related allowance	27,286	27,574
Ending Balance	27,515	27,881
Commercial, industrial and other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	389,230	336,735
Ending Balance: Individually evaluated for impairment, related allowance	8	7
Ending Balance	2,592	1,742	1,768	2,313
Commercial, industrial and other \| Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Ending Balance: Individually evaluated for impairment	2,509	1,360
Ending Balance: Collectively evaluated for impairment	384,213	335,375
Ending Balance: Loans acquired with deteriorated credit quality	2,508	0
Total Loans	389,230	336,735
Ending Balance: Individually evaluated for impairment, related allowance	8	7
Ending Balance: Collectively evaluated for impairment, related allowance	2,584	1,735
Ending Balance	2,592	1,742
Equipment finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	90,791	87,925
Ending Balance: Individually evaluated for impairment, related allowance	12	14
Ending Balance	947	987	1,042	630
Equipment finance \| Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Ending Balance: Individually evaluated for impairment	327	331
Ending Balance: Collectively evaluated for impairment	90,464	87,594
Ending Balance: Loans acquired with deteriorated credit quality	0	0
Total Loans	90,791	87,925
Ending Balance: Individually evaluated for impairment, related allowance	12	14
Ending Balance: Collectively evaluated for impairment, related allowance	935	973
Ending Balance	947	987
Real estate - residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	335,290	329,854
Ending Balance: Individually evaluated for impairment, related allowance	4	4
Ending Balance	1,564	1,566	1,589	1,557
Real estate - residential mortgage \| Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Ending Balance: Individually evaluated for impairment	715	730
Ending Balance: Collectively evaluated for impairment	334,177	329,124
Ending Balance: Loans acquired with deteriorated credit quality	398	0
Total Loans	335,290	329,854
Ending Balance: Individually evaluated for impairment, related allowance	4	4
Ending Balance: Collectively evaluated for impairment, related allowance	1,560	1,562
Ending Balance	1,564	1,566
Real estate - construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	332,995	319,545
Ending Balance: Individually evaluated for impairment, related allowance	0	0
Ending Balance	2,887	3,015	2,932	2,731
Real estate - construction \| Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Ending Balance: Individually evaluated for impairment	0	0
Ending Balance: Collectively evaluated for impairment	329,566	319,545
Ending Balance: Loans acquired with deteriorated credit quality	3,429	0
Total Loans	332,995	319,545
Ending Balance: Individually evaluated for impairment, related allowance	0	0
Ending Balance: Collectively evaluated for impairment, related allowance	2,887	3,015
Ending Balance	2,887	3,015
Home equity and consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	339,815	328,609
Ending Balance: Individually evaluated for impairment, related allowance	6	6
Ending Balance	2,474	2,497	$ 2,496	$ 2,520
Home equity and consumer \| Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Ending Balance: Individually evaluated for impairment	700	727
Ending Balance: Collectively evaluated for impairment	338,573	327,882
Ending Balance: Loans acquired with deteriorated credit quality	542	0
Total Loans	339,815	328,609
Ending Balance: Individually evaluated for impairment, related allowance	6	6
Ending Balance: Collectively evaluated for impairment, related allowance	2,468	2,491
Ending Balance	$ 2,474	$ 2,497

Financial Asset Acquired with Credit Deterioration

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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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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

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-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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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
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-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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