LOANS - Schedule of Industry and Rate Sensitivity (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	$ 2,061,878	$ 2,144,850
Computer Programming, Data Processing & Other Computer Related Services
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	409,644	394,193
Management & Public Relations Services
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	257,404	339,179
Industrial Inorganic Chemicals
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	141,941	0
Public Warehousing & Storage
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	124,836	107,029
Engineering, Architectural, and Surveying
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	110,984	124,201
Metal Cans & Shipping Containers
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	110,478	118,456
Offices & Clinics of Doctors of Medicine
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	104,064	106,993
Surgical, Medical & Dental Instruments & Supplies
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	99,444	102,182
Electronic Components & Accessories
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	78,114	24,000
Insurance Agents, Brokers and Service
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	68,577	75,410
Telephone Communications
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	58,233	61,210
Miscellaneous Health & Allied Services, not elsewhere classified
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	52,307	78,908
Miscellaneous Equipment Rental & Leasing
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	49,589	49,776
Electric Work
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	41,170	43,175
Medical & Dental Laboratories
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	40,477	41,344
Research, Development & Testing Services
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	29,648	45,610
Metal Forgings & Stampings
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	29,390	0
Home Health Care Services
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	28,914	29,361
Motor Vehicles and Motor Vehicle Parts & Supplies
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	28,545	28,815
Legal Services
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	26,420	0
Petroleum and Petroleum Products
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	24,709	24,923
Grocery Stores
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	22,937	23,248
Coating, Engraving and Allied Services
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	19,456	47,249
Schools & Educational Services, not elsewhere classified
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	19,325	19,586
Chemicals & Allied Products
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	14,595	15,002
Miscellaneous Business Services
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	12,953	164,033
Drugs
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	12,952	15,923
Mailing, Reproduction, Commercial Art and Photography and Stenographic
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	12,879	14,755
Machinery, Equipment & Supplies
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	12,080	0
Miscellaneous Plastic Products
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	9,940	10,000
Offices and Clinics of Other Health Practitioners
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	9,873	10,098
Nonferrous Foundries (Castings)
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt	$ 0	$ 30,191