GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 506,206	$ 506,206	$ 256,105
Other Intangible Assets	23,107	29,286
Total goodwill and other intangible assets	529,313	535,492
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Other Intangible Assets	22,215	28,016
Other identifiable Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Other Intangible Assets	$ 892	$ 1,270