CREDIT QUALITY ASSESSMENT - Allowance for credit loss activity (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period			$ 165,367	$ 56,132	$ 56,132
Initial allowance on acquired Revere PCD loans			0	18,628	18,628
Provision/ (credit) for credit losses	$ (4,204)	$ 58,686	(38,912)	83,155	85,669
Loan charge-offs			(3,485)	(1,039)	(1,819)
Loan recoveries			991	860	1,012
Net charge-offs			(2,494)	(179)	(807)
Balance at period end	123,961	$ 163,481	123,961	163,481	165,367
Revision of Prior Period, Reclassification, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				2,762	2,762
Balance at period end	0		0
Revision of Prior Period, Accounting Standards Update, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				$ 2,983	$ 2,983
Balance at period end	$ 0		$ 0