Retirement Plans Other Changes in Plan Assets (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Amortization of prior service cost	$ 58	$ 72	$ 242
Amortization of actuarial gain (loss)	(17,079)	40,148	(6,941)
Income tax (expense) benefit	6,507	(15,562)	2,366
Other comprehensive income (loss) on pension and postretirement obligations	(10,514)	24,658	(4,333)
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)	(17,945)	35,366
Amortization of prior service cost	58	72
Amortization of actuarial gain (loss)	1,384	4,344
Income tax (expense) benefit	6,308	(15,394)
Other comprehensive income (loss) on pension and postretirement obligations	(10,195)	24,388
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)	(483)	438
Amortization of prior service cost	0	0
Amortization of actuarial gain (loss)	(35)	0
Income tax (expense) benefit	199	(168)
Other comprehensive income (loss) on pension and postretirement obligations	$ (319)	$ 270