Employee Benefit Plans (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Benefit Plan
Periodic costs for employee retirement benefit plans
Service Cost	$ 2,198	$ 1,574	$ 1,396
Interest Cost	2,417	2,261	2,228
Expected Return on Assets	(2,458)	(2,283)	(2,020)
Amortization of Unrecognized Losses
Amortization of Unrecognized Prior Service Cost	1,549	565	506
Amortization of Transition Obligation	10	10	10
Net Periodic Benefit Cost	3,716	2,128	2,120
Other Benefits Plan
Periodic costs for employee retirement benefit plans
Service Cost	1,784	1,306
Interest Cost	1,868	1,604
Expected Return on Assets	(1,258)	(1,026)
Amortization of Unrecognized Losses	135	135
Amortization of Unrecognized Prior Service Cost	1,765	878
Amortization of Transition Obligation
Net Periodic Benefit Cost	4,294	2,897
Other Benefit Plan
Periodic costs for employee retirement benefit plans
Service Cost			1,025
Interest Cost			1,335
Expected Return on Assets			(759)
Amortization of Unrecognized Losses			135
Amortization of Unrecognized Prior Service Cost			531
Amortization of Transition Obligation
Net Periodic Benefit Cost			$ 2,267