LOANS (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Deferred fees	$ 0		$ 9,143
Allowance for credit losses	232,726	$ 232,192	47,576	$ 47,671
Net loans and leases	9,102,332		8,424,464
Reverse mortgage, fair value	12,500		16,600	17,700
Accrued interest receivable on loans and leases	36,400		31,500
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	857,494		1,016,500
Allowance for credit losses	8,454	9,171	1,381	1,330
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	1,168,891		1,128,731
Allowance for credit losses	20,870	21,317	7,387	7,715
Financing Receivable Portfolio Segment, Including Reverse Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	9,335,058		8,481,183
Commercial and industrial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	2,902,815		2,046,798
Allowance for credit losses	148,529	144,225	22,849	24,504
Owner-occupied commercial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	1,344,494		1,296,466
Allowance for credit losses	10,384	8,956	4,616	4,504
Commercial mortgages | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	2,167,508		2,222,976
Allowance for credit losses	34,259	38,397	7,452	6,737
Construction | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	666,317		581,082
Allowance for credit losses	10,230	$ 10,126	3,891	$ 2,881
Commercial small business leases | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	227,539		$ 188,630
Paycheck Protection Program, CARES Act | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 954,200