Acquisitions and Dispositions (Details) - USD ($) $ in Millions	Dec. 16, 2016	Dec. 08, 2016	Dec. 01, 2016	Aug. 31, 2016	Apr. 25, 2016	Apr. 15, 2016
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						$ 46.9
South Bearhead Creek and Burr Ferry Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Participation Interest Sold in Oil and Gas Properties		25.00%				75.00%
Proceeds from Sale of Oil and Gas Property and Equipment		$ 7.1				$ 46.9
Buyer's Assumption of ARO		$ 2.4				$ 6.5
Masters Creek 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					$ 0.1
Buyer's Assumption of ARO					$ 8.1
Sun TSH 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				$ 0.9
Buyer's Assumption of ARO				$ 1.8
Lake Washington 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			$ 37.0
Buyer's Assumption of ARO			$ 30.5
Royalty Package 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	$ 0.5