BORROWINGS (Subordinated detbt) (Detail) - USD ($) $ in Thousands		3 Months Ended	6 Months Ended
	Nov. 05, 2019	Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Subordinated Borrowing [Line Items]
Subordinated Debt			$ 230,301		$ 209,406
Repayments of Subordinated Debt			10,310	$ 0
Subordinated Debt [Member]
Subordinated Borrowing [Line Items]
Subordinated Debt	$ 175,000		231,000		200,000
Purchase accounting premium			2,052		1,894
Subordinated debt maturity date	Jan. 01, 2029
Subordinated debt fixed interest rate	4.25%
Debt issuance costs	$ 2,900		2,751		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%
Subordinated Debt [Member] | Revere acquisition [Member]
Subordinated Borrowing [Line Items]
Subordinated Debt			$ 31,000
Purchase accounting premium			$ 200
Subordinated debt maturity date			Sep. 30, 2026
Subordinated debt fixed interest rate			5.625%
Description of Variable Rate Basis			3 month LIBOR plus 441 basis points
Basis spread variable interest rate			4.41%
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			, the interest rate resets quarterly to an amount equal to 3 month LIBOR plus 467 basis points
Basis spread variable interest rate			4.67%