CREDIT QUALITY ASSESSMENT (Information by Credit Risk Rating Indicators for Those Remaining Segments of Loan Portfolio) (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	$ 10,333,935	$ 6,705,232
Residential real estate: | Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	1,173,857	1,149,327
Residential real estate: | Residential construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	175,123	146,279
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	$ 521,999	466,764
Homogeneous Loan Pools
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		1,762,370
Homogeneous Loan Pools | Residential real estate: | Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		1,149,327
Homogeneous Loan Pools | Residential real estate: | Residential construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		146,279
Homogeneous Loan Pools | Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		466,764
Homogeneous Loan Pools | Performing loans:
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		1,744,158
Homogeneous Loan Pools | Performing loans: | Residential real estate: | Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		1,135,586
Homogeneous Loan Pools | Performing loans: | Residential real estate: | Residential construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		146,279
Homogeneous Loan Pools | Performing loans: | Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		462,293
Homogeneous Loan Pools | Non-performing loans: | 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		0
Homogeneous Loan Pools | Non-performing loans: | Non-accruing
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		16,768
Homogeneous Loan Pools | Non-performing loans: | Restructured Loans | Restructured loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		1,444
Homogeneous Loan Pools | Non-performing loans: | Residential real estate: | Residential mortgage | 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		0
Homogeneous Loan Pools | Non-performing loans: | Residential real estate: | Residential mortgage | Non-accruing
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		12,661
Homogeneous Loan Pools | Non-performing loans: | Residential real estate: | Residential mortgage | Restructured Loans | Restructured loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		1,080
Homogeneous Loan Pools | Non-performing loans: | Residential real estate: | Residential construction | 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		0
Homogeneous Loan Pools | Non-performing loans: | Residential real estate: | Residential construction | Non-accruing
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		0
Homogeneous Loan Pools | Non-performing loans: | Residential real estate: | Residential construction | Restructured Loans | Restructured loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		0
Homogeneous Loan Pools | Non-performing loans: | Consumer | 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		0
Homogeneous Loan Pools | Non-performing loans: | Consumer | Non-accruing
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		4,107
Homogeneous Loan Pools | Non-performing loans: | Consumer | Restructured Loans | Restructured loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases		$ 364