Supplemental Disclosures (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Summary of current accrued liabilities
Total accrued liabilities	$ 174,348	$ 101,460
Other	4,418	3,011
Accrued evaluated and unproved and unevaluated property costs [Member]
Summary of current accrued liabilities
Total accrued liabilities	105,347	54,273
Accrued support equipment and facilities costs [Member]
Summary of current accrued liabilities
Total accrued liabilities	14,823	15,139
Accrued lease operating expenses [Member]
Summary of current accrued liabilities
Total accrued liabilities	12,611	16,009
Accrued interest on debt [Member]
Summary of current accrued liabilities
Total accrued liabilities	8,345	6,541
Accrued asset retirement obligations [Member]
Summary of current accrued liabilities
Total accrued liabilities	1,176	915
Accrued partners' share of joint interest charges [Member]
Summary of current accrued liabilities
Total accrued liabilities	$ 27,628	$ 5,572