Loans Receivable and Allowance for Loan Losses - Summary of PCD Loans (Details) - USD ($) $ in Thousands		12 Months Ended
	Jul. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Apr. 01, 2019
Financing Receivable, Allowance for Credit Losses [Line Items]
Gross amortized cost basis at July 31, 2020					$ 822,400
Interest component of expected cash flows (accretable difference)	$ 455
Fair value of acquired loans at July 31, 2020	1,766,115
Allowance for credit losses on PCD loans	(13,586)
Net PCD loans		$ 1,752,529	$ 0	$ 0
SB One Bancorp
Financing Receivable, Allowance for Credit Losses [Line Items]
Gross amortized cost basis at July 31, 2020	315,784
Interest component of expected cash flows (accretable difference)	(7,988)
Fair value of acquired loans at July 31, 2020	307,796
Allowance for credit losses on PCD loans	(13,586)
Net PCD loans	$ 294,210	$ 294,210