Pension and Postretirement Benefits other than Pensions Postretirement Benefits Recognized in Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	$ (82,040)	$ (73,061)	$ (71,874)	$ (55,148)
Postretirement Benefit Costs [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actuarial loss	32,870	32,279
Prior service credit	19,838	21,368
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	$ (13,032)	$ (10,911)