Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Consolidated Statements of Comprehensive Income
Net income	$ 16,924	$ 13,355	$ 46,441	$ 36,175
Net unrealized loss on securities available-for-sale:
Net unrealized holding loss on securities arising during the period	(1,286)	(3,796)	(7,889)	(3,194)
Reclassification adjustment for gain on sales of securities included in net income			(1,332)	(1,604)
Net unrealized loss on securities available-for-sale	(1,286)	(3,796)	(9,221)	(4,798)
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	585	448	1,754	3,077
Net actuarial loss adjustment on pension plans and other postretirement benefits	585	448	1,754	27,363
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	34	32	103	67
Prior service cost adjustment on pension plans and other postretirement benefits	34	32	103	(3,470)
Reclassification adjustment for loss on cash flow hedge included in net income		56		151
Total other comprehensive (loss) income, net of tax	(667)	(3,260)	(7,364)	19,246
Comprehensive income	$ 16,257	$ 10,095	$ 39,077	$ 55,421