Other Comprehensive Income/Loss (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net unrealized loss on securities available-for-sale before tax amount:
Net unrealized holding loss on securities arising during the year	$ (16,202)	$ (2,040)	$ (5,181)
Reclassification adjustment for gain on sales of securities included in net income	(2,057)	(8,477)
Net unrealized loss on securities available-for-sale	(18,259)	(10,517)
Net actuarial loss adjustment on pension plans and other postretirement benefits before tax amount:
Net actuarial loss adjustment arising during the year	68,150	14,141	(55,530)
Reclassification adjustment for net actuarial loss included in net income	3,610	5,447	8,592
Net actuarial loss adjustment on pension plans and other postretirement benefits	71,760	19,588	(46,938)
Prior service cost adjustment on pension plans and other postretirement benefits before tax amount:
Prior service cost adjustment arising during the year		(5,463)
Reclassification adjustment for prior service cost included in net income	213	152	92
Prior service cost adjustment on pension plans and other postretirement benefits		(5,311)
Reclassification adjustment for loss on cash flow hedge included in net income, before tax amount		261	330
Total other comprehensive income, before tax amount	53,714	4,021	(51,697)
Net unrealized loss on securities available-for-sale, tax benefit (expense):
Net unrealized holding loss on securities arising during the year	5,717	720	1,827
Reclassification adjustment for gains included in net income	725	2,987
Net unrealized loss on securities available-for-sale	6,442	3,707
Net actuarial loss adjustment on pension plans and other postretirement benefits, tax benefit (expense):
Net actuarial loss adjustment arising during the year	(23,970)	(4,998)	19,570
Reclassification adjustment for net actuarial loss included in net income	(1,275)	(1,920)	(3,028)
Net actuarial loss adjustment on pension plans and other postretirement benefits	(25,245)	(6,918)	16,542
Prior service cost adjustment on pension plans and other postretirement benefits, tax benefit (expense):
Prior service cost adjustment arising during the year		1,925
Reclassification adjustment for prior service cost included in net income	(71)	(54)	(32)
Prior service cost adjustment on pension plans and other postretirement benefits	(18,874)	1,871
Reclassification adjustment for loss on cash flow hedge included in net income, tax benefit (expense)		(110)	(140)
Total other comprehensive income, tax benefit (expense)		(1,450)	18,197
Net unrealized loss on securities available-for-sale:
Net unrealized holding loss on securities arising during the year	(10,485)	(1,320)	(3,354)
Reclassification adjustment for gains included in net income	(1,332)	(5,490)
Net unrealized loss on securities available-for-sale	(11,817)	(6,810)	(3,354)
Net actuarial loss adjustment on pension plans and other postretirement benefits:
Net actuarial loss adjustment arising during the year	44,180	9,143	(35,960)
Reclassification adjustment for net actuarial loss included in net income	2,335	3,527	5,564
Net actuarial loss adjustment on pension plans and other postretirement benefits	46,515	12,670	(30,396)
Prior service cost adjustment on pension plans and other postretirement benefits:
Prior service cost adjustment arising during the year		(3,538)
Reclassification adjustment for prior service cost included in net income	142	98	60
Prior service cost adjustment on pension plans and other postretirement benefits		(3,440)
Reclassification adjustment for loss on cash flow hedge included in net income		151	190
Total other comprehensive income (loss), net of tax	$ 34,840	$ 2,571	$ (33,500)