GOODWILL AND INTANGIBLE ASSETS (Information Concerning Intangible Assets with Finite Life) (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Total estimated amortization expense	$ 57,185,000
Core Deposits
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	135,300,000	$ 135,300,000
Accumulated Amortization	88,109,000	73,336,000
Total estimated amortization expense	47,191,000	61,964,000
Other Amortizable Intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	15,240,000	15,349,000
Accumulated Amortization	5,246,000	3,644,000
Total estimated amortization expense	$ 9,994,000	$ 11,705,000