Employee Benefit Plans (Details 1) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Amounts recognized in the consolidated balance sheets
Employee benefit plan obligations	$ (53,131)	$ (52,972)
Pension Benefits
Amounts recognized in the consolidated balance sheets
Accrued expenses	(202)	(213)
Employee benefit plan obligations	(17,831)	(22,158)
Net amount recognized	(18,033)	(22,371)
Postretirement Benefits
Amounts recognized in the consolidated balance sheets
Accrued expenses	(1,241)	(1,211)
Employee benefit plan obligations	(34,813)	(30,347)
Net amount recognized	$ (36,054)	$ (31,558)