Acquisition of Florida Chemical Company, Inc. - Pro Forma Results of Operations (Details) (Florida Chemical Company, Inc [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Florida Chemical Company, Inc [Member]
Business Acquisition [Line Items]
Revenue	$ 98,388	$ 97,173	$ 294,559	$ 301,382
Net income	$ 8,968	$ 11,129	$ 27,313	$ 28,115
Earnings per common share:
Basic (in dollars per share)	$ 0.17	$ 0.23	$ 0.54	$ 0.59
Diluted (in dollars per share)	$ 0.16	$ 0.22	$ 0.51	$ 0.55