Business Acquisition and Disposition Proforma Results (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Business Acquisition [Line Items]
Net Income (Loss) Attributable to Parent	$ 34,355	$ 687	$ (9,782)	$ 6,826	$ 4,849	$ 5,735	$ 8,928	$ 1,069	$ 32,086	$ 20,581	$ 36,314
Refusol [Member]
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue									567,087	622,388
Net Income (Loss) Attributable to Parent									(6,100)
Business Acquisition, Pro Forma Net Income (Loss)									$ 27,380	$ 19,978
Business Acquisition, Pro Forma Earnings Per Share, Basic									$ 0.69	$ 0.51
Business Acquisition, Pro Forma Earnings Per Share, Diluted									$ 0.67	$ 0.50