ALLOWANCE FOR CREDIT LOSSES ON LOANS AND FINANCE LEASES - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
	Sep. 01, 2020	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable Allowance For Credit Losses [Line Items]
Financing Receivable Allowance For Credit Losses				$ 269,030	$ 385,887	$ 155,139	$ 196,362
Increase (decrease) in ACL				116,900	230,800
Provision (release) for credit losses				(61,720)	168,717	40,225
Increase (decrease) in provision for credit losses			$ 1,100
Increase (decrease) in net charge-offs				7,300
Recoveries				25,573	16,662	16,139
Charge-off					47,900	81,400
Off-Balance Sheet, Credit Loss, Liability, Credit Loss Expense (Reversal)				(3,568)	1,183	(412)
Off-Balance Sheet, Credit Loss, Liability				$ 1,537	5,105	0	412
Allowance For Loan And Lease Losses Writeoffs Net Period Increase Decrease Percent				15.00%
Residential Portfolio Segment [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Financing Receivable Allowance For Credit Losses				$ 74,837	120,311	44,806	50,794
Increase (decrease) in ACL				(45,500)
Provision (release) for credit losses				(16,957)	22,427	14,091
Net charge-offs		$ 28,500
Increase (decrease) in net charge-offs				19,000
Recoveries		17,000		4,777	1,519	2,663
Residential Portfolio Segment [Member] | Bulk Sale Of Nonaccrual Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Net charge-offs		23,100
Charge-off		23,100
Residential Portfolio Segment [Member] | Nonaccrual loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Financing Receivable Allowance For Credit Losses		20,900
Provision (release) for credit losses		$ 2,100
Commercial Portfolio Segment [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Increase (decrease) in ACL				(61,600)
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Financing Receivable Allowance For Credit Losses				4,048	5,380	2,370	3,592
Provision (release) for credit losses				(1,408)	2,105	(1,496)
Recoveries				163	184	665
Commercial Portfolio Segment [Member] | Nonaccrual loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Recoveries				5,200
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Financing Receivable Allowance For Credit Losses				52,771	109,342	39,194	55,581
Provision (release) for credit losses				(55,358)	81,125	(1,697)
Recoveries				281	1,936	398
Consumer Portfolio Segment [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Financing Receivable Allowance For Credit Losses				103,090	112,910	53,571	$ 53,849
Provision (release) for credit losses				20,552	56,433	43,023
Recoveries				13,576	9,831	$ 8,859
Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Increase (decrease) in ACL				(9,800)
Provision (release) for credit losses				(20,600)
Increase (decrease) in net charge-offs				6,300
Charge-off				$ 30,400
Non-PCD | Santander [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Provision (release) for credit losses	$ 37,500
Non-PCD | Santander [Member] | Residential Portfolio Segment [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Provision (release) for credit losses	13,600
Non-PCD | Santander [Member] | Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Provision (release) for credit losses	9,200
Non-PCD | Santander [Member] | Consumer Portfolio Segment [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Provision (release) for credit losses	$ 10,200
Financial Asset Acquired with Credit Deterioration [Member] | Santander [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Provision (release) for credit losses					28,700
ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Increase (decrease) in ACL					$ 81,200