CREDIT QUALITY ASSESSMENT (Summary information on the allowance for credit loss activity) (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 56,132	$ 53,486	$ 53,486
Provision (credit)	24,469	(128)	4,684
Loan charge-offs	(654)	(356)	(2,668)
Loan recoveries	108	87	630
Net charge-offs	(546)	(269)	(2,038)
Balance at end of period	85,800	53,089	56,132
Initial allowance on purchased credit deteriorated loans at adoption of ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	2,762	0	0
Balance at end of period			2,762
Transition impact of adopting ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 2,983	$ 0	0
Balance at end of period			$ 2,983