Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Consolidated Statements of Comprehensive Income
Net income	$ 15,665	$ 12,824	$ 29,517	$ 22,820
Net unrealized (loss) gain on securities available-for-sale:
Net unrealized holding (loss) gain on securities arising during the period	(6,733)	1,416	(6,603)	602
Reclassification adjustment for gain on sales of securities included in net income	(1,332)		(1,332)	(1,604)
Net unrealized (loss) gain on securities available-for-sale	(8,065)	1,416	(7,935)	(1,002)
Net actuarial loss adjustment on pension plans and other postretirement benefits:
Net actuarial loss adjustment arising during the period				24,286
Reclassification adjustment for net actuarial loss included in net income	542	428	1,169	2,629
Net actuarial loss adjustment on pension plans and other postretirement benefits	542	428	1,169	26,915
Prior service cost adjustment on pension plans and other postretirement benefits:
Prior service cost adjustment arising during the period				(3,537)
Reclassification adjustment for prior service cost included in net income	35	33	69	35
Prior service cost adjustment on pension plans and other postretirement benefits	35	33	69	(3,502)
Reclassification adjustment for loss on cash flow hedge included in net income		47		95
Total other comprehensive (loss) income, net of tax	(7,488)	1,924	(6,697)	22,506
Comprehensive income	$ 8,177	$ 14,748	$ 22,820	$ 45,326