Borrowings (Details Textual) (Fifth Third Loan, USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Fifth Third Loan
Borrowing (Textual) [Abstract]
Term Loan Renewal Period			3 years
Principal payments	$ 150
Basis point	5.00%
Effective interest rate	5.20%
Interest to be accrued	LIBOR plus 5% per annum
REG Danville principal payment to Fifth Third	50.00%
Excess Cash Flow Payment	$ 591	$ 1,458
Agreement starting period	Nov. 03, 2011