Retirement Plans (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Prior service cost, net of amortization	$ 242	$ 467	$ 467
Amortization of actuarial gain (loss)	(6,941)	(14,810)	2,271
Income tax (expense) benefit	2,366	5,674	(1,106)
Other comprehensive income (loss) on pension and postretirement obligations	(4,333)	(8,669)	1,632
Pension Plans, Defined Benefit [Member]
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Net gain (loss)	(9,735)	(16,711)
Prior service cost, net of amortization	72	72
Amortization of actuarial gain (loss)	3,073	2,024
Income tax (expense) benefit	2,324	5,780
Other comprehensive income (loss) on pension and postretirement obligations	(4,266)	(8,835)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Net gain (loss)	(279)	(123)
Prior service cost, net of amortization	170	395
Amortization of actuarial gain (loss)	0	0
Income tax (expense) benefit	42	(106)
Other comprehensive income (loss) on pension and postretirement obligations	$ (67)	$ 166