SUBORDINATED DEBENTURES (Additional Information) (Detail) - USD ($) $ in Thousands		3 Months Ended
	Nov. 05, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Subordinated Borrowing [Line Items]
Subordinated Debt		$ 199,046		$ 209,406
Repayments of Subordinated Debt		10,310	$ 0
Subordinated Debt [Member]
Subordinated Borrowing [Line Items]
Subordinated Debt	$ 175,000	200,000		200,000
Purchase accounting premium		1,846		1,894
Subordinated debt maturity date	Jan. 01, 2029
Subordinated debt fixed interest rate	4.25%
Debt issuance costs	$ 2,900	2,800		2,885
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%
Junior subordinated debt securities [Member]
Subordinated Borrowing [Line Items]
Subordinated Debt				10,310
Purchase accounting premium				$ 87
Repayments of Subordinated Debt		$ 10,300
Junior subordinated debt securities [Member] | 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	three month 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
Basis spread variable interest rate	2.62%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debt [Member] | WashingtonFirst Bankshares Inc [Member]
Subordinated Borrowing [Line Items]
Description of Variable Rate Basis		at 3 month LIBOR plus 467 basis points
Basis spread variable interest rate		4.67%