LOANS (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses	$ 204,818	$ 228,804	$ 139,073	$ 47,576
Net loans and leases	8,373,766	8,795,935
Reverse mortgage, fair value	9,400	10,100	15,800
Accrued interest receivable on loans and leases	36,100	37,600
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	681,022	774,455
Allowance for credit losses	5,702	6,893	11,593	1,381
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	1,140,034	1,165,917
Allowance for credit losses	18,797	18,160	20,370	7,387
Financing Receivable Portfolio Segment, Including Reverse Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	8,578,584	9,024,739
Commercial and industrial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	2,398,535	2,700,418
Allowance for credit losses	125,870	150,875	65,771	22,849
Owner-occupied commercial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	1,333,989	1,332,727
Allowance for credit losses	9,617	9,615	9,541	4,616
Commercial mortgages | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	1,975,966	2,086,062
Allowance for credit losses	30,545	31,071	26,600	7,452
Construction | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	784,101	716,275
Allowance for credit losses	14,287	12,190	$ 5,198	$ 3,891
Commercial small business leases | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	264,937	248,885
Paycheck Protection Program, CARES Act | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 526,800	$ 751,200