Long - Term Debt (Details Textual) (USD $) In Thousands, unless otherwise specified	12 Months Ended			1 Months Ended		12 Months Ended				12 Months Ended			1 Months Ended	12 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Nov. 30, 2010 8.625 % Senior Notes due 2017 [Member]	Jan. 31, 2010 8.625 % Senior Notes due 2017 [Member]	Dec. 31, 2011 8.625 % Senior Notes due 2017 [Member]	Dec. 31, 2010 8.625 % Senior Notes due 2017 [Member]	Nov. 17, 2010 8.625 % Senior Notes due 2017 [Member]	Jan. 26, 2010 8.625 % Senior Notes due 2017 [Member]	Dec. 31, 2011 6.75 % Senior Subordinated Notes due 2014 [Member]	Dec. 31, 2010 6.75 % Senior Subordinated Notes due 2014 [Member]	Dec. 15, 2004 6.75 % Senior Subordinated Notes due 2014 [Member]	Feb. 28, 2010 8.25 % Senior Subordinated Notes due 2011 [Member]	Dec. 31, 2010 8.25 % Senior Subordinated Notes due 2011 [Member]	Dec. 05, 2001 8.25 % Senior Subordinated Notes due 2011 [Member]	Dec. 31, 2011 Bank debt [Member]	Feb. 21, 2012 Bank debt [Member]	Oct. 31, 2011 Bank debt [Member]	Apr. 26, 2011 Bank debt [Member]	Dec. 31, 2010 Bank debt [Member]	Feb. 21, 2012 Letter of Credit [Member]	Dec. 31, 2011 Letter of Credit [Member]
Long Term Debt (Textual) [Abstract]
Credit facility initial date																Apr. 26, 2011
Credit Facility																			$ 700,000
Credit facility maturing with Syndicated Bank Group																Sep. 15, 2014
Maturity of new credit facility if note issue under 2004 indenture are retired on or before April 15,2014																Apr. 26, 2015
Aggregate Principal amount of Senior Subordinated Notes								100,000	275,000
Initial bank and Availability under facility																	302,855	400,000
Outstanding borrowing under bank credit facility																45,000	70,000				27,145	61,145
Weighted average interest rate																						4.25%
Covenants of Bank credit facility																(i) maintain a ratio of consolidated debt to consolidated EBITDA, as defined in the credit agreement, for the preceding four quarterly periods of not greater than 3.25 to 1 and (ii) maintain a ratio of EBITDA to consolidated Net Interest, as defined in the credit agreement, for the preceding four quarterly periods of not less than 3.0 to 1.0.
Period in which outstanding amount has to be repaid to cure the deficiency																10 days
Period in which bank has to add new properties to the borrowing base and has to grant mortgage to banks																30 days
Period over which deficiency can be repaid in installments																90 days
Period over which deficiency can be repaid in installments maximum																6 months
Oil and gas reserve as a proportion of discounted present value of the future net cash flow, for Mortgage																80.00%
Debt to EBITDA ratio, as defined in credit agreement																not greater than 3.25 for preceding four quarter
EBITDA to consolidated Net Interest, as defined in credit agreement																not less than 3.0 for preceding four quarter
Debt to EBITDA ratio	1.09 to 1
EBITDA to consolidated Net interest ratio	70.37 to 1
Proceeds from issuance of senior notes		375,000		98,277	265,299					195,500
Proportion of 2017 Notes which company can redeem before February 1, 2013						35.00%
Accrued interest	14,059	14,062				13,477				563
Long-term debt	620,000	575,000				375,000	375,000			200,000	200,000	200,000			200,000	45,000				0
Total cost of the redemption													202,382
Cost of redemption excluding accrued and unpaid interest													200,483
Accrued and unpaid interest													1,899
Redemption resulted in a charge to earnings	(607)	(1,820)												1,820
Price to be paid in case of redemption, maximum, as percentage to principal amount											103.375%
Price to be paid in case of redemption, minimum, as percentage to principal amount											100.00%
Deferred financing costs, net of accumulated amortization	14,437	14,764
Applies effective interest rate							8.80%				7.10%
Total interest cost incurred	$ 51,322	$ 42,975	$ 46,934