OTHER COMPREHENSIVE INCOME : OTHER COMPREHENSIVE INCOME (LOSS)-Reclassifications (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities gains (losses)										$ 34	$ 17	$ (3)
Income tax expense										(19,883)	(10,392)	(14,189)
NET INCOME		$ 8,344	$ 8,162	$ 8,232	$ 13,675	$ 7,114	$ 8,398	$ 6,923	$ 7,761	38,413	30,196	33,772
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
NET INCOME										(1,195)	(4,909)	(463)
Unrealized Gains and Losses on Available-for-Sale Securities | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities gains (losses)										34	17	(3)
Income tax expense										(13)	(6)	1
NET INCOME										21	11	(2)
Retirement Plans | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Change in funded status of post retirement benefits	[1]									(1,992)	(8,066)	(756)
Income tax expense										776	3,146	295
NET INCOME										$ (1,216)	$ (4,920)	$ (461)

[1] Included in the computation of net periodic benefit cost which is included in salaries and benefits. (see Footnote 15 for additional details).