CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Pension and other post retirement obligations:
Amortization of actuarial losses included in net periodic pension cost, gross	$ 1,012	$ 925	$ 2,021	$ 1,849
Tax effect	(394)	(359)	(784)	(717)
Amortization of actuarial losses included in net periodic pension cost, net	618	566	1,237	1,132
Amortization of prior service cost included in net periodic pension cost, gross	(30)	(243)	(61)	(485)
Tax effect	12	94	24	188
Amortization of prior service cost included in net periodic pension cost, net	(18)	(149)	(37)	(297)
Other comprehensive income related to pension and other post retirement obligations, net of taxes	600	417	1,200	835
Unrealized gains on securities:
Net unrealized holding (losses) gains arising during period, gross	(50,777)	51,397	(69,649)	44,388
Tax effect	19,081	(19,644)	26,179	(17,221)
Net unrealized holding (losses) gains arising during period, net	(31,696)	31,753	(43,470)	27,167
Reclassification adjustment for net gains included in net income, gross	(16,007)	0	(63,799)	0
Tax effect	6,175	0	24,019	0
Reclassification adjustment for gains included in net income, net	(9,832)	0	(39,780)	0
Other comprehensive loss related to unrealized gain on available-for-sale securities, net of taxes	(41,528)	31,753	(83,250)	27,167
Other comprehensive (loss)/income, net of tax	(40,928)	32,170	(82,050)	28,002
Net income	21,122	21,071	41,363	39,897
Comprehensive (loss)/income	(19,806)	53,241	(40,687)	67,899
Accumulated Other Comprehensive Income By Component: [Abstract]
Unrealized loss for pension and other postretirement obligations	(43,272)		(43,272)		(45,232)
Tax effect	16,687		16,687		17,447
Net unrealized loss for pension and other postretirement obligations	(26,585)		(26,585)		(27,785)
Unrealized (loss)/gain on available-for-sale securities	(1,992)		(1,992)		131,456
Tax effect	861		861		(49,337)
Net unrealized (loss)/gain on available-for-sale securities	(1,131)		(1,131)		82,119
Accumulated other comprehensive income	$ (27,716)		$ (27,716)		$ 54,334