Other Comprehensive Income/Loss (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Changes in accumulated other comprehensive loss components
Balance at the beginning of the period	$ (72,299)		$ (73,090)
Other comprehensive (loss) income, net of tax	(7,488)	1,924	(6,697)	22,506
Balance at the end of the period	(79,787)		(79,787)
Net unrealized gain (loss) on securities available-for-sale
Changes in accumulated other comprehensive loss components
Balance at the beginning of the period	7,581		7,451
Other comprehensive (loss) income, net of tax	(8,065)		(7,935)
Balance at the end of the period	(484)		(484)
Net actuarial loss on pension plans and other postretirement benefits
Changes in accumulated other comprehensive loss components
Balance at the beginning of the period	(76,488)		(77,115)
Other comprehensive (loss) income, net of tax	542		1,169
Balance at the end of the period	(75,946)		(75,946)
Prior service cost on pension plans and other postretirement benefits
Changes in accumulated other comprehensive loss components
Balance at the beginning of the period	(3,392)		(3,426)
Other comprehensive (loss) income, net of tax	35		69
Balance at the end of the period	$ (3,357)		$ (3,357)