CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension and other post retirement obligations:
Amortization of actuarial losses/(gains) included in net periodic pension cost, gross	$ 5,514	$ (7,236)	$ (13,904)
Tax effect	(2,108)	2,774	5,374
Amortization of actuarial losses/(gains) included in net periodic pension cost, net	3,406	(4,462)	(8,530)
Amortization of prior service cost included in net periodic pension cost, gross	(136)	(170)	(1,698)
Tax effect	52	65	657
Amortization of prior service cost included in net periodic pension cost, net	(84)	(105)	(1,041)
Other comprehensive income/(loss) related to pension and other post retirement obligations, net of taxes	3,322	(4,567)	(9,571)
Unrealized (losses)/gains on securities:
Net unrealized holding (losses)/gains arising during period, gross	(24,042)	(9,209)	106,040
Tax effect	9,328	2,289	(39,203)
Net unrealized holding (losses)/gains arising during period, net	(14,714)	(6,920)	66,837
Reclassification adjustment for net losses included in net income, gross	0	4	0
Tax effect	0	(2)	0
Reclassification adjustment for net losses included in net income, net	0	2	0
Other comprehensive (loss)/income related to unrealized (losses)/gains on available-for-sale securities, net of taxes	(14,714)	(6,918)	66,837
Other comprehensive (loss)/income, net of tax	(11,392)	(11,485)	57,266
Net income	103,812	91,230	91,353
Comprehensive income	92,420	79,745	148,619
Accumulated Other Comprehensive Income By Component:
Unrealized loss for pension and other postretirement obligations	(28,969)	(34,347)	(26,941)
Tax effect	11,008	13,064	10,225
Net unrealized loss for pension and other postretirement obligations	(17,961)	(21,283)	(16,716)
Unrealized gain on available-for-sale securities	41,793	65,835	75,039
Tax effect	(15,989)	(25,317)	(27,603)
Net unrealized gain on available-for-sale securities	25,804	40,518	47,436
Accumulated other comprehensive income	$ 7,843	$ 19,235	$ 30,720