SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (New Accounting Policies and Accounting Standards Adopted) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other service charges and fees									$ 13,123	$ 11,518	$ 11,449
Other operating expense									134,682	131,073	132,518
Income tax expense									18,758	34,596	26,273
Net income	$ 15,792	$ 15,193	$ 14,224	$ 14,277	$ 4,288	$ 11,812	$ 12,025	$ 13,079	59,486	41,204	46,992
Available-for-sale Securities, Equity Securities	$ 826				825				826	825
Impact of adoption of new accounting standards					(139)					(139)
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other service charges and fees									600
Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impact of adoption of new accounting standards									(1,836)
Unrealized gains recorded in AOCI				$ 500
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability									55,900
Scenario, Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other operating expense									135,687	131,817	133,563
Income tax expense									17,753	33,852	25,228
Net income									59,486	41,204	46,992
Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other operating expense									(1,005)	(744)	(1,045)
Income tax expense									1,005	744	1,045
Net income									$ 0	0	$ 0
Accumulated Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impact of adoption of new accounting standards					$ (139)					$ (139)