Revolving Credit Agreement (Details) (USD $)	0 Months Ended	1 Months Ended		2 Months Ended	6 Months Ended
	Feb. 08, 2012	Feb. 28, 2012	Jan. 30, 2012	Aug. 31, 2012	Jun. 30, 2012	Aug. 14, 2012	Jan. 31, 2012	Dec. 31, 2011
Revolving Credit Agreement (Textual) [Abstract]
Borrowing base		$ 125,000,000						$ 125,000,000
Credit facility, outstanding					1,300,000	90,000,000	123,000,000	113,000,000
Revolving Credit Agreement (Additional Textual) [Abstract]
Company amended and restated its senior secured revolving credit agreement					December 2011
Credit Agreement, maturity date					Dec. 31, 2016
The borrowing base under the Credit Agreement determined					semi-annually
Outstanding letters of credit					60,000,000
Additional outstanding borrowings under the Credit Agreement			10,000,000	30,000,000
Repayment of the outstanding under the Credit Agreement in full	123,000,000	123,000,000
Available for additional borrowings					63,700,000
Outstanding borrowings bore interest effective rate					3.30%
Percentage of reserves required to maintain					100.00%
Total debt outstanding to EBITDA					4.0
February 2012 [Member]
Revolving Credit Agreement (Textual) [Abstract]
Borrowing base		100,000,000
Federal Reserve System [Member]
Revolving Credit Agreement (Textual) [Abstract]
Borrowings interest rate					1.00%
Base rate loan [Member]
Revolving Credit Agreement (Textual) [Abstract]
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 weighted average of rates used in overnight federal funds transactions with members of the Federal Reserve System plus 1.0% or (ii) the prime rate for Comerica Bank then in effect or (iii) a daily adjusted LIBOR rate plus 1.0% plus, in each case, an amount from 0.375% to 1.75% of such outstanding loan depending on the level of borrowings under the agreement.
LIBOR Rate [Member]
Revolving Credit Agreement (Textual) [Abstract]
Borrowings interest rate					1.00%
Eurodollar Loan [Member]
Revolving Credit Agreement (Textual) [Abstract]
Borrowings interest rate description					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 interest rate appearing on Page BBAM of the Bloomberg Financial Markets Information Service by (B) a percentage equal to 100% minus the maximum rate during such interest calculation period at which Comerica Bank 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 1.375% to 2.75% of such outstanding loan depending on the level of borrowings under the agreement.
Maximum [Member]
Revolving Credit Agreement (Textual) [Abstract]
Senior secured revolving credit maximum facility								400,000,000
Credit facility fee					0.50%
Maximum [Member] | Base rate loan [Member]
Revolving Credit Agreement (Textual) [Abstract]
Additional interest rate					1.75%
Maximum [Member] | Eurodollar Loan [Member]
Revolving Credit Agreement (Textual) [Abstract]
Additional interest rate					2.75%
Minimum [Member]
Revolving Credit Agreement (Textual) [Abstract]
Senior secured revolving credit maximum facility								$ 150,000,000
Credit facility fee					0.375%
Minimum [Member] | Base rate loan [Member]
Revolving Credit Agreement (Textual) [Abstract]
Additional interest rate					0.375%
Minimum [Member] | Eurodollar Loan [Member]
Revolving Credit Agreement (Textual) [Abstract]
Additional interest rate					1.375%