OTHER COMPREHENSIVE INCOME : OTHER COMPREHENSIVE INCOME (LOSS)-Reclassifications (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities gains (losses)										$ 17	$ (3)	$ 423
Income tax expense										(10,392)	(14,189)	(13,767)
NET INCOME		$ 7,114	$ 8,398	$ 6,923	$ 7,761	$ 9,181	$ 8,272	$ 8,488	$ 7,831	30,196	33,772	31,534
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
NET INCOME										(4,909)	(463)	(10,315)
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)										17	(3)	423
Income tax expense										(6)	1	(169)
NET INCOME										11	(2)	254
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]									(8,066)	(756)	(17,615)
Income tax expense										3,146	295	7,046
NET INCOME										$ (4,920)	$ (461)	$ (10,569)

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