SUBORDINATED DEBENTURES (Additional Information) (Detail) - USD ($) $ in Thousands		12 Months Ended
	Nov. 05, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2003
Subordinated Borrowing [Line Items]
Subordinated Debt		$ 209,406	$ 37,425
Repayments of Subordinated Debt		0	0	$ 30,000
Subordinated Debt [Member]
Subordinated Borrowing [Line Items]
Subordinated Debt	$ 175,000	200,000	25,000
Purchase accounting premium		1,894	2,023
Subordinated debt maturity date	Jan. 01, 2029
Subordinated debt fixed interest rate	4.25%
Debt issuance costs	$ 2,900	2,885	0
Subordinated Debt [Member] | WashingtonFirst Bankshares Inc [Member]
Subordinated Borrowing [Line Items]
Subordinated Debt		25,000
Purchase accounting premium		$ 2,200
Maturity period		10 years
Subordinated debt maturity date		Oct. 15, 2025
Subordinated debt fixed interest rate		6.00%
Description of Variable Rate Basis		LIBOR plus 467 basis points
Subordinated debt variable interest rate		4.67%
Junior subordinated debt securities
Subordinated Borrowing [Line Items]
Subordinated Debt		$ 10,310	10,310		$ 10,300
Purchase accounting premium		$ 87	$ 92
Subordinated debt maturity date					Sep. 08, 2033
Description of Variable Rate Basis					LIBOR plus 3.15%
Subordinated debt variable interest rate		5.06%			3.15%
Junior subordinated debt securities | WashingtonFirst Bankshares Inc [Member]
Subordinated Borrowing [Line Items]
Subordinated Debt		$ 10,300
Purchase accounting premium		$ 100
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debt [Member]
Subordinated Borrowing [Line Items]
Description of Variable Rate Basis	LIBOR, or an alternative benchmark rate as determined pursuant to the terms of the indenture for the notes in the event LIBOR has been discontinued by November 15, 2024, plus 262 basis points
Subordinated debt variable interest rate	2.62%