Asset Retirement Obligations (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation: Beginning of Year		$ 140,874	[1],[2]	$ 122,124
Asset Retirement Obligation, Liabilities Incurred	[3]	21,293		14,471
Asset Retirement Obligation, Liabilities Settled	[4]	(57,100)		(24,781)
Asset Retirement Obligation, Accretion Expense		7,795		5,091
Asset Retirement Obligation, Revision of Estimate		10,445		23,969
Asset Retirement Obligation: End of Year	[1],[2]	123,307		140,874
Asset Retirement Obligations Assets Held-for-sale Noncurrent		26,241		241
Asset Retirement Obligation, Current		$ 932		$ 3,300

[1] Balance as of December 31, 2016, included $26.2 million of asset retirement obligations associated with oil and gas properties held for sale, specifically the Company’s outside-operated Eagle Ford shale assets. There were no material asset retirement obligations related to assets held for sale as of December 31, 2015.

[2] Balances as of December 31, 2016, and 2015, included $932,000 and $3.3 million, respectively, related to the Company’s current asset retirement obligation liability, which is recorded in accounts payable and accrued expenses on the accompanying balance sheets.

[3] Reflects liabilities incurred through drilling activities and acquisitions of drilled wells.

[4] Reflects liabilities settled through plugging and abandonment activities and divestitures of properties.