Other Comprehensive Income/Loss (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accumulated Other Comprehensive Income (Loss)
Net unrealized gain on securities available-for-sale	$ 7,451	$ 14,261
Net actuarial loss on pension plans and other postretirement benefits	(77,115)	(89,785)
Prior service cost on pension plans and other postretirement benefits	(3,426)	14
Loss on cash flow hedge		(151)
Accumulated other comprehensive loss	(73,090)	(75,661)
Other Comprehensive (Loss) Income:
Net unrealized gain on securities available-for-sale	(6,810)	(3,354)	(597)
Net actuarial loss on pension plans and other postretirement benefits	12,670	(30,396)	(12,070)
Prior service cost on pension plans and other postretirement benefits	(3,440)	60	95
Loss on cash flow hedge	151	190	190
Total other comprehensive income (loss), net of tax	$ 2,571	$ (33,500)	$ (12,382)