Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands		Jun. 30, 2015	Dec. 31, 2014
Property and Equipment
Proved oil and gas properties		$ 5,876,399	$ 5,826,995
Unproved oil and gas properties		71,118	64,903
Furniture, fixtures, and other equipment		44,563	42,257
Less - Accumulated depreciation, depletion, and amortization		(4,704,508)	(3,839,118)
Property and Equipment, Net		1,287,572	2,095,037
Accounts Payable and Accrued Liabilities
Trade accounts payable	[1]	12,361	31,153
Accrued operating expenses		8,352	10,784
Accrued payroll costs		7,432	8,715
Asset retirement obligation - current portion		7,197	10,709
Accrued taxes		5,385	2,957
Other payables		4,859	3,926
Total accounts payable and accrued liabilities		$ 45,586	$ 68,244

[1] Included in “trade accounts payable” are liabilities of approximately $1.6 million and $13.7 million at June 30, 2015 and December 31, 2014, respectively, for outstanding checks.