ALLOWANCE FOR CREDIT LOSSES ON LOANS AND FINANCE LEASES - Carrying Amount of Portfolios (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable Allowance For Credit Losses [Line Items]
Amortized cost of loans	$ 11,777,289	$ 9,002,205
Allowance for credit losses	$ 385,887	$ 155,139	$ 196,362	$ 231,843
Allowance for loan and lease losses, numerator [Member] | Amortized cost, denominator [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses to amortized cost	3.28%	1.72%
Residenital Mortgage Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Amortized cost of loans	$ 3,521,954	$ 2,933,773
Allowance for credit losses	$ 120,311	$ 44,806	50,794	58,975
Residenital Mortgage Loans [Member] | Allowance for loan and lease losses, numerator [Member] | Amortized cost, denominator [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses to amortized cost	3.42%	1.53%
Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Amortized cost of loans	$ 3,202,590	$ 2,230,876
Allowance for credit losses	$ 37,944	$ 15,198	32,546	48,871
Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member] | Allowance for loan and lease losses, numerator [Member] | Amortized cost, denominator [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses to amortized cost	1.18%	0.68%
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Amortized cost of loans	$ 2,230,602	$ 1,444,586
Allowance for credit losses	$ 109,342	$ 39,194	55,581	48,493
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member] | Allowance for loan and lease losses, numerator [Member] | Amortized cost, denominator [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses to amortized cost	4.90%	2.71%
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Amortized cost of loans	$ 212,500	$ 111,317
Allowance for credit losses	$ 5,380	$ 2,370	3,592	4,522
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Allowance for loan and lease losses, numerator [Member] | Amortized cost, denominator [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses to amortized cost	2.53%	2.13%
Consumer Portfolio Segment [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Amortized cost of loans	$ 2,609,643	$ 2,281,653
Allowance for credit losses	$ 112,910	$ 53,571	$ 53,849	$ 70,982
Consumer Portfolio Segment [Member] | Allowance for loan and lease losses, numerator [Member] | Amortized cost, denominator [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses to amortized cost	4.33%	2.35%