Supplemental Disclosures (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Summary of current accrued liabilities
Total accrued liabilities	$ 109,502	$ 63,987
Other	5,635	3,586
Accrued evaluated and unproved and unevaluated property costs [Member]
Summary of current accrued liabilities
Total accrued liabilities	86,259	52,605
Accrued support equipment and facilities costs [Member]
Summary of current accrued liabilities
Total accrued liabilities	4,290	0
Accrued stock-based compensation [Member]
Summary of current accrued liabilities
Total accrued liabilities	0	56
Accrued lease operating expenses [Member]
Summary of current accrued liabilities
Total accrued liabilities	9,034	6,251
Accrued interest on borrowings under Credit Agreement [Member]
Summary of current accrued liabilities
Total accrued liabilities	206	141
Accrued asset retirement obligations [Member]
Summary of current accrued liabilities
Total accrued liabilities	311	175
Accrued partners' share of joint interest charges [Member]
Summary of current accrued liabilities
Total accrued liabilities	$ 3,767	$ 1,173