Acquisitions - Pro Forma Consolidated Results (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Business Acquisition [Line Items]
Revenues	$ 102,231	$ 95,907	$ 100,532	$ 95,618	$ 91,092	$ 90,477	$ 91,249	$ 86,631	$ 394,288	$ 359,449	$ 296,755
Sales, Pro Forma									431,861	396,767
Net income									19,710	23,044	12,460
Net income, Pro Forma									24,296	22,033
Earnings per common share: basic	$ 0.02	$ 0.17	$ 0.14	$ 0.14	$ 0.12	$ 0.11	$ 0.19	$ 0.19	$ 0.47	$ 0.59	$ 0.35
Earnings per common share: basic, Pro Forma									$ 0	$ 0
Earnings per common share: diluted	$ 0.01	$ 0.17	$ 0.14	$ 0.14	$ 0.12	$ 0.11	$ 0.18	$ 0.18	$ 0.46	$ 0.58	$ 0.35
Earnings per common share: diluted, Pro Forma									$ 0	$ 0
BioSphere [Member]
Business Acquisition [Line Items]
Sales, Pro Forma											317,382
Net income, Pro Forma											$ 7,258
Earnings per common share: basic, Pro Forma											$ 0.21
Earnings per common share: diluted, Pro Forma											$ 0.20