Quarterly report pursuant to sections 13 or 15(d)

Property and Equipment (Details Textual)

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Property and Equipment (Details Textual) (USD $)
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Dec. 31, 2011
Property and Equipment (Textual) [Abstract]          
Pump equipment     $ 6,800,000   $ 7,400,000
Depreciation expense included in accumulated depreciation 2,500,000   2,500,000   2,200,000
Depreciation expense $ 1,500,000 $ 1,600,000 $ 2,903,000 $ 3,167,000