Supplemental Disclosures (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Summary of current accrued liabilities
Other	$ 2,804	$ 2,410
Total accrued liabilities	48,512	59,179
Accrued evaluated and unproved and unevaluated property costs [Member]
Summary of current accrued liabilities
Total accrued liabilities	38,297	45,592
Accrued support equipment and facilities costs [Member]
Summary of current accrued liabilities
Total accrued liabilities	467	1,382
Accrued stock-based compensation [Member]
Summary of current accrued liabilities
Total accrued liabilities	0	65
Accrued lease operating expenses [Member]
Summary of current accrued liabilities
Total accrued liabilities	5,823	5,218
Accrued interest on borrowings under Credit Agreement [Member]
Summary of current accrued liabilities
Total accrued liabilities	186	255
Accrued asset retirement obligations [Member]
Summary of current accrued liabilities
Total accrued liabilities	804	660
Accrued partners share of joint interest charges [Member]
Summary of current accrued liabilities
Total accrued liabilities	$ 131	$ 3,597