COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Before Tax Amount [Abstract]
Unrealized (losses) gains arising during holding period, Before tax amount	$ 6,225	$ (1,484)	$ 6,605	$ 21,221
Reclassification adjustment for net gains realized in net income, Before tax amount	(33)	(18)	(88)	(19)
Recognized employee benefit plan net periodic benefit cost, Before tax amount	1,797	738	5,391	2,214
Other comprehensive (loss) income, Before tax amount	7,989	(764)	11,908	23,416
Tax Effect [Abstract]
Unrealized (losses) gains arising during holding period, Tax effect	(2,382)	567	(2,550)	(8,130)
Reclassification adjustment for net gains realized in net income, Tax effect	13	7	34	7
Recognized employee benefit plan net periodic benefit cost, Tax effect	(687)	(283)	(2,061)	(847)
Other comprehensive (loss) income, Tax effect	(3,056)	291	(4,577)	(8,970)
Net of Tax Amount [Abstract]
Unrealized (losses) gains arising during holding period, Net of tax amount	3,843	(917)	4,055	13,091
Reclassification adjustment for net gains realized in net income, Net of tax amount	(20)	(11)	(54)	(12)
Recognized employee benefit plan net periodic benefit cost, Net of tax amount	1,110	455	3,330	1,367
Other comprehensive (loss) income, net of tax	4,933	(473)	7,331	14,446
Net income	34,343	28,778	106,322	88,090
Comprehensive income	$ 39,276	$ 28,305	$ 113,653	$ 102,536