Loans and Other Real Estate - Age Analysis of Past Due Loans, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 5,140,940	$ 4,460,447
Commercial, secured by real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	3,589,593	3,057,779
Commercial, industrial and other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	431,934	336,735
Equipment finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	111,076	87,925
Real estate - residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	335,191	329,854
Real estate - construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	335,169	319,545
Home equity and consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	337,977	328,609
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	24,322	12,022
Current	5,107,870	4,447,773
Total Loans	5,132,192	4,459,795
Recorded Investment Greater than 89 Days and Still Accruing	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial, secured by real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	14,480	4,196
Current	3,569,008	3,052,931
Total Loans	3,583,488	3,057,127
Recorded Investment Greater than 89 Days and Still Accruing	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Commercial, industrial and other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,488	1,166
Current	429,502	335,569
Total Loans	430,990	336,735
Recorded Investment Greater than 89 Days and Still Accruing	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Equipment finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	530	1,047
Current	110,546	86,878
Total Loans	111,076	87,925
Recorded Investment Greater than 89 Days and Still Accruing	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Real estate - residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,464	2,630
Current	331,337	327,224
Total Loans	334,801	329,854
Recorded Investment Greater than 89 Days and Still Accruing	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Real estate - construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	967	0
Current	333,418	319,545
Total Loans	334,385	319,545
Recorded Investment Greater than 89 Days and Still Accruing	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Home equity and consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,393	2,983
Current	334,059	325,626
Total Loans	337,452	328,609
Recorded Investment Greater than 89 Days and Still Accruing	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	6,808	4,843
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | 30-59 Days Past Due | Commercial, secured by real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,578	1,477
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | 30-59 Days Past Due | Commercial, industrial and other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	353	173
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | 30-59 Days Past Due | Equipment finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	166	533
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | 30-59 Days Past Due | Real estate - residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,138	743
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | 30-59 Days Past Due | Real estate - construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | 30-59 Days Past Due | Home equity and consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,573	1,917
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,889	1,222
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | 60-89 Days Past Due | Commercial, secured by real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,200	639
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | 60-89 Days Past Due | Commercial, industrial and other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	71	243
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | 60-89 Days Past Due | Equipment finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	80	13
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | 60-89 Days Past Due | Real estate - residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	251	111
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | 60-89 Days Past Due | Real estate - construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | 60-89 Days Past Due | Home equity and consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	287	216
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Greater Than 89 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	15,625	5,957
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Greater Than 89 Days | Commercial, secured by real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	9,702	2,080
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Greater Than 89 Days | Commercial, industrial and other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,064	750
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Greater Than 89 Days | Equipment finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	284	501
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Greater Than 89 Days | Real estate - residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,075	1,776
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Greater Than 89 Days | Real estate - construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	967	0
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Greater Than 89 Days | Home equity and consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 1,533	$ 850