DEBT (Details) (USD $) In Thousands, unless otherwise specified			1 Months Ended	3 Months Ended		12 Months Ended				0 Months Ended	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	May 31, 2011 2010 Credit Facility item	Mar. 31, 2013 2010 Credit Facility	Mar. 31, 2012 2010 Credit Facility	Dec. 31, 2010 2010 Credit Facility	Nov. 30, 2012 2010 Credit Facility	Nov. 30, 2010 2010 Credit Facility	Apr. 16, 2010 2010 Credit Facility	May 09, 2013 2010 Credit Facility Subsequent event	Mar. 31, 2013 2010 Credit Facility Minimum	Mar. 31, 2012 2010 Credit Facility Minimum	Mar. 31, 2013 2010 Credit Facility Maximum	Mar. 31, 2012 2010 Credit Facility Maximum
Debt
Maximum borrowing capacity							$ 130,000	$ 150,000	$ 100,000
Available working capital borrowings				23,500
Drawdowns during the period						1,500				1,000
Remaining borrowing capacity				28,750
Number of consecutive semi-annual reductions in total commitment			11
Amount of semi-annual reductions in maximum borrowing capacity through the maturity date			5,000
Borrowing capacity on maturity date				0
Repayment of the outstanding debt
2015				1,250
2016				100,000
Total debt	$ 101,250	$ 101,250		$ 101,250
Effective interest rate including the range of interest rates on the debt but excluding the impact of unused commitment fees
Effective Interest Rate (as a percent)				3.21%	3.27%
Range of Interest Rates (excluding impact of unused commitment fees) (as a percent)											3.20%	3.24%	3.21%	3.30%