Acquisitions and Dispositions Acquisitions and Dispositions (Details) - USD ($) $ in Thousands		9 Months Ended
	Jan. 24, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 22, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments for (Proceeds from) Other Investing Activities		$ 7,036	$ 0
AWP Olmos Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Sale of Oil and Gas Property and Equipment	$ 27,000
Buyer's Assumption of ARO	$ 6,300
Bay De Chene [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Purchase and sale contract				$ 16,300
Long-term liability reclassified to current		3,800
Cash to be released for purchase and sale contract		9,300
Other Current Liabilities [Member] | Bay De Chene [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Purchase and sale contract		8,000
Other Noncurrent Liabilities [Member] | Bay De Chene [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Purchase and sale contract		$ 1,300