CREDIT QUALITY ASSESSMENT - Allowance for credit loss activity (Detail) - USD ($) $ in Thousands		12 Months Ended
	Apr. 01, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year		$ 56,132	$ 53,486	$ 45,257
Initial allowance on Revere PCD loans	$ 18,600	18,628	0	0
Provision for credit losses		85,669	4,684	9,023
Loan charge-offs		(1,819)	(2,668)	(1,416)
Loan recoveries		1,012	630	622
Net charge-offs		(807)	(2,038)	(794)
Balance at period end		165,367	56,132	53,486
Initial allowance on PCD loans at adoption of ASC 326
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year		2,762	0	0
Balance at period end			2,762	0
Transition impact of adopting ASC 326
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year		$ 2,983	0	0
Balance at period end			$ 2,983	$ 0