CREDIT QUALITY ASSESSMENT - Credit Quality of Loan Portfolio (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Total past due		$ 27,748
Non-accrual loans		38,632
Loans acquired with deteriorated credit quality		13,084
Current loans		6,625,768
Total	$ 10,400,509	6,705,232
Commercial investor real estate
Financing Receivable, Past Due [Line Items]
Total	3,634,720
Commercial owner-occupied real estate
Financing Receivable, Past Due [Line Items]
Total	1,642,216
Commercial AD&C
Financing Receivable, Past Due [Line Items]
Total	1,050,973
Residential mortgage
Financing Receivable, Past Due [Line Items]
Total	1,105,179
Residential construction
Financing Receivable, Past Due [Line Items]
Total	182,619
Commercial real estate: | Commercial investor real estate
Financing Receivable, Past Due [Line Items]
Total past due		932
Non-accrual loans		8,437
Loans acquired with deteriorated credit quality		9,544
Current loans		2,150,243
Total	3,634,720	2,169,156
Commercial real estate: | Commercial owner-occupied real estate
Financing Receivable, Past Due [Line Items]
Total past due		316
Non-accrual loans		4,148
Loans acquired with deteriorated credit quality		0
Current loans		1,284,213
Total	1,642,216	1,288,677
Commercial real estate: | Commercial AD&C
Financing Receivable, Past Due [Line Items]
Total past due		0
Non-accrual loans		829
Loans acquired with deteriorated credit quality		0
Current loans		683,181
Total	1,050,973	684,010
Commercial Business
Financing Receivable, Past Due [Line Items]
Non-accrual loans		8,450
Total	8,595,457	4,942,862
Commercial Business | Commercial business
Financing Receivable, Past Due [Line Items]
Total past due		1,278
Non-accrual loans		8,450
Loans acquired with deteriorated credit quality		2,539
Current loans		788,752
Total	2,267,548	801,019
Residential real estate: | Residential mortgage
Financing Receivable, Past Due [Line Items]
Total past due		19,394
Non-accrual loans		12,661
Loans acquired with deteriorated credit quality		8
Current loans		1,117,264
Total	1,105,179	1,149,327
Residential real estate: | Residential construction
Financing Receivable, Past Due [Line Items]
Total past due		1,614
Non-accrual loans		0
Loans acquired with deteriorated credit quality		0
Current loans		144,665
Total	182,619	146,279
Consumer
Financing Receivable, Past Due [Line Items]
Total past due		4,214
Non-accrual loans		4,107
Loans acquired with deteriorated credit quality		993
Current loans		457,450
Total	$ 517,254	466,764
30-59 days
Financing Receivable, Past Due [Line Items]
Total past due		19,986
30-59 days | Commercial real estate: | Commercial investor real estate
Financing Receivable, Past Due [Line Items]
Total past due		932
30-59 days | Commercial real estate: | Commercial owner-occupied real estate
Financing Receivable, Past Due [Line Items]
Total past due		316
30-59 days | Commercial real estate: | Commercial AD&C
Financing Receivable, Past Due [Line Items]
Total past due		0
30-59 days | Commercial Business | Commercial business
Financing Receivable, Past Due [Line Items]
Total past due		908
30-59 days | Residential real estate: | Residential mortgage
Financing Receivable, Past Due [Line Items]
Total past due		14,853
30-59 days | Residential real estate: | Residential construction
Financing Receivable, Past Due [Line Items]
Total past due		280
30-59 days | Consumer
Financing Receivable, Past Due [Line Items]
Total past due		2,697
60-89 days
Financing Receivable, Past Due [Line Items]
Total past due		7,762
60-89 days | Commercial real estate: | Commercial investor real estate
Financing Receivable, Past Due [Line Items]
Total past due		0
60-89 days | Commercial real estate: | Commercial owner-occupied real estate
Financing Receivable, Past Due [Line Items]
Total past due		0
60-89 days | Commercial real estate: | Commercial AD&C
Financing Receivable, Past Due [Line Items]
Total past due		0
60-89 days | Commercial Business | Commercial business
Financing Receivable, Past Due [Line Items]
Total past due		370
60-89 days | Residential real estate: | Residential mortgage
Financing Receivable, Past Due [Line Items]
Total past due		4,541
60-89 days | Residential real estate: | Residential construction
Financing Receivable, Past Due [Line Items]
Total past due		1,334
60-89 days | Consumer
Financing Receivable, Past Due [Line Items]
Total past due		1,517
> 90 days
Financing Receivable, Past Due [Line Items]
Total past due		0
> 90 days | Commercial real estate: | Commercial investor real estate
Financing Receivable, Past Due [Line Items]
Total past due		0
> 90 days | Commercial real estate: | Commercial owner-occupied real estate
Financing Receivable, Past Due [Line Items]
Total past due		0
> 90 days | Commercial real estate: | Commercial AD&C
Financing Receivable, Past Due [Line Items]
Total past due		0
> 90 days | Commercial Business | Commercial business
Financing Receivable, Past Due [Line Items]
Total past due		0
> 90 days | Residential real estate: | Residential mortgage
Financing Receivable, Past Due [Line Items]
Total past due		0
> 90 days | Residential real estate: | Residential construction
Financing Receivable, Past Due [Line Items]
Total past due		0
> 90 days | Consumer
Financing Receivable, Past Due [Line Items]
Total past due		$ 0