Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Pension Benefit Plan
Periodic costs for employee retirement benefit plans
Service Cost	$ 575	$ 549	$ 1,150	$ 1,099
Interest Cost	617	604	1,234	1,208
Expected Return on Assets	(723)	(614)	(1,447)	(1,229)
Amortization of Unrecognized Losses	408	388	816	775
Amortization of Unrecognized Prior Service Cost (Credit)	3	3	5	5
Amortization of Transition Obligation
Net Periodic Benefit Cost	880	930	1,758	1,858
Other Benefits Plan
Periodic costs for employee retirement benefit plans
Service Cost	335	446	669	892
Interest Cost	398	467	797	934
Expected Return on Assets	(405)	(315)	(811)	(629)
Amortization of Unrecognized Losses	517	442	1,033	883
Amortization of Unrecognized Prior Service Cost (Credit)	(432)		(864)
Amortization of Transition Obligation		34		68
Net Periodic Benefit Cost	$ 413	$ 1,074	$ 824	$ 2,148