CREDIT QUALITY ASSESSMENT (Additional Information) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Troubled Debt Restructurings Restructured Accruing	$ 1,600	$ 2,100
Other real estate owned	1,584	2,253
Mortgage Loans in Process of Foreclosure, Amount	200
Non-accrual loans	33,583	26,336
Loans and Leases Receivable, Net of Deferred Income, Total	6,571,634	4,314,248
Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income, Total	53,615	25,019
WashingtonFirst Bankshares Inc [Member] | Special Mention [Member] | Performing Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income, Total	3,900
WashingtonFirst Bankshares Inc [Member] | Substandard | Credit impaired loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income, Total	24,300
WashingtonFirst Bankshares Inc [Member] | Substandard | Performing Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income, Total	7,200
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other real estate owned	800
Consumer Portfolio Segment [Member] | Acquisition Development and Construction Mortgage Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	3,200
Consumer Portfolio Segment [Member] | WashingtonFirst Bankshares Inc [Member] | Performing Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	1,300
Restructured Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Troubled Debt Restructurings Specific Allowance	600	200
Financing Receivable Troubled Debt Restructurings Restructured Accruing	2,000	2,800
Financing Receivable Troubled Debt Restructurings Restructured Non Accruing	5,400	6,200
Financing Receivable Troubled Debt Restructurings Balance	7,400	9,000
Additional Financing Receivable Troubled Debt Restructurings Restructured	$ 0	$ 100