Other Comprehensive Income/Loss (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Changes in accumulated other comprehensive loss components
Balance at the beginning of the period	$ (35,092)	$ (72,299)	$ (38,250)	$ (73,090)
Other comprehensive income, net of tax	4,891	(7,488)	8,049	(6,697)
Balance at the end of the period	(30,201)	(79,787)	(30,201)	(79,787)
Net unrealized (loss) gain on securities available-for-sale
Changes in accumulated other comprehensive loss components
Balance at the beginning of the period	(1,373)	7,581	(4,366)	7,451
Other comprehensive income, net of tax	4,699	(8,065)	7,692	(7,935)
Balance at the end of the period	3,326	(484)	3,326	(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	(30,465)	(76,488)	(30,600)	(77,115)
Other comprehensive income, net of tax	161	542	296	1,169
Balance at the end of the period	(30,304)	(75,946)	(30,304)	(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	(3,254)	(3,392)	(3,284)	(3,426)
Other comprehensive income, net of tax	31	35	61	69
Balance at the end of the period	$ (3,223)	$ (3,357)	$ (3,223)	$ (3,357)