Revolving Credit Agreement (Details Textual) (USD $)	12 Months Ended							1 Months Ended			1 Months Ended	12 Months Ended					12 Months Ended		12 Months Ended						12 Months Ended							12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 20, 2012	Sep. 30, 2012	Jan. 31, 2012	May 31, 2011	Sep. 30, 2012 Second amended credit agreement [Member]	Sep. 28, 2012 Second amended credit agreement [Member]	Dec. 31, 2011 Second amended credit agreement [Member]	Sep. 30, 2012 Third amended credit agreement [Member]	Dec. 31, 2012 Third amended credit agreement [Member]	Sep. 28, 2012 Third amended credit agreement [Member]	Mar. 14, 2013 Subsequent Event [Member]	Mar. 11, 2013 Subsequent Event [Member]	Dec. 31, 2012 Subsequent Event [Member]	Dec. 31, 2012 Base rate loan [Member]	Dec. 31, 2012 LIBOR rate [Member]	Dec. 31, 2012 Eurodollar Loan [Member]	Dec. 31, 2012 Maximum [Member]	Dec. 20, 2012 Maximum [Member]	Feb. 28, 2012 Maximum [Member]	Dec. 31, 2011 Maximum [Member] Second amended credit agreement [Member]	Sep. 28, 2012 Maximum [Member] Third amended credit agreement [Member]	Dec. 31, 2012 Maximum [Member] Base rate loan [Member]	Dec. 31, 2012 Maximum [Member] Eurodollar Loan [Member]	Dec. 31, 2012 Minimum [Member]	Dec. 20, 2012 Minimum [Member]	Feb. 28, 2012 Minimum [Member]	Dec. 31, 2011 Minimum [Member] Second amended credit agreement [Member]	Sep. 28, 2012 Minimum [Member] Third amended credit agreement [Member]	Dec. 31, 2012 Minimum [Member] Base rate loan [Member]	Dec. 31, 2012 Minimum [Member] Eurodollar Loan [Member]
Revolving Credit Agreement (Textual) [Abstract]
Additional borrowings for working capital requirements	$ 150,000,000					$ 10,000,000										$ 30,000,000
Senior secured revolving credit maximum facility									400,000,000				500,000,000		255,000,000
Conforming borrowing base	220,000,000			180,000,000									165,000,000
Borrowings under the credit agreement																							400,000,000							125,000,000
Borrowing base	255,000,000																				215,000,000	125,000,000		200,000,000				200,000,000	100,000,000		125,000,000
Borrowings interest rate																		1.00%
Additional interest rate																									2.25%	3.25%						0.75%	1.75%
Credit facility fee																				0.50%							0.375%
Repay deficit in agreement Period	6 months
Borrowings interest rate description																	If the Company borrows funds as a base rate loan, such borrowings will bear interest at a rate equal to the higher of (i) the prime rate for such day or (ii) the Federal Funds Effective Rate on such day, plus 0.50% or (iii) the daily adjusting LIBOR rate plus 1.0% plus, in each case, an amount from 0.75% to 2.25% of such outstanding loan depending on the level of borrowings under the Credit Agreement		If the Company borrows funds as a Eurodollar loan, such borrowings will bear interest at a rate equal to (i) the quotient obtained by dividing (A) the LIBOR rate by (B) a percentage equal to 100% minus the maximum rate during such interest calculation period at which RBC is required to maintain reserves on Eurocurrency Liabilities (as defined in Regulation D of the Board of Governors of the Federal Reserve System) plus (ii) an amount from 1.75% to 3.25% of such outstanding loan depending on the level of borrowings under the Credit Agreement.
Net cash proceeds from secondary public offering	146,510,000	592,000	20,652,000								25,000,000
Conforming borrowing base description												The borrowing base will automatically be reduced to an amount equal to the conforming borrowing base on the earlier of (i) December 31, 2013 or (ii) the closing of a secondary public offering of equity interests by the Company that results in net cash proceeds to the Company in an amount greater than or equal to $25 million.
Conforming borrowing base date												Dec. 31, 2013
Company amended and restated its senior secured revolving credit agreement								2012-9-28
Borrowed under credit agreement	150,000,000					123,000,000	25,000,000			113,000,000						180,000,000
Additional deferred loan cost	100,000				800,000									300,000
Deferred Loan fees	800,000
Deferred Loan Costs	1,600,000
Outstanding letters of credit	1,100,000													1,300,000		1,300,000
Available for additional borrowings	$ 63,900,000															$ 73,700,000
Outstanding borrowings bore interest effective rate	3.30%
Revolving Credit Agreement (Additional Textual) [Abstract]
Credit Agreement, maturity date	Dec. 29, 2016
The borrowing base under the Credit Agreement determined	semi-annually
Percentage of reserves required to maintain	100.00%
Total debt outstanding to EBITDA	4.0
Current ratio	1.0
Federal Funds Effective Plus Rate	0.50%