Summary of Significant Accounting Policies (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Property and Equipment
Proved oil and gas properties	$ 5,850,175		$ 5,826,995
Unproved oil and gas properties	64,577		64,903
Furniture, fixtures, and other equipment	44,088		42,257
Less - Accumulated depreciation, depletion, and amortization	(4,402,460)		(3,839,118)
Property and Equipment, Net	1,556,380		2,095,037
Accounts Payable and Accrued Liabilities
Trade accounts payable	43,912	[1]	31,153	[1]
Accrued operating expenses	7,699		10,784
Accrued payroll costs	6,080		8,715
Asset retirement obligation - current portion	6,879		10,709
Accrued taxes	3,897		2,957
Other payables	5,082		3,926
Total accounts payable and accrued liabilities	$ 73,549		$ 68,244

[1] Included in “trade accounts payable” are liabilities of approximately $35.7 million and $13.7 million at March 31, 2015 and December 31, 2014, respectively, for outstanding checks.