INCOME TAXES, Components of Net Deferred Tax Liability (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Components of net deferred tax liability [Abstract]
Allowance for loan losses	$ 11,675	$ 18,366
Employee benefits	4,216	6,311
Debt extinguishment	0	299
Other, net	0	5,202
Deferred tax asset	15,891	30,178
Investment securities	22,690	32,839
Tax-deductible goodwill	39,154	43,504
Loan origination costs	6,109	8,228
Depreciation	2,372	71
Mortgage servicing rights	330	548
Pension	13,228	18,194
Other, net	542	0
Deferred tax liability	84,425	103,384
Net deferred tax liability	$ (68,534)	$ (73,206)