Acquisitions and Divestitures Haynesville/Cotton Valley Divestiture (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
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	$ 13.8	$ 678.9	$ 243.6
Gain (Loss) on Disposition of Oil and Gas Property	$ 1.2	3.9	25.0
Haynesville Divestiture [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Definitive Agreement Agreed Upon Sales Price			735.0
Proceeds from Sale of Oil and Gas Property and Equipment		633.9
Escrow Deposit			32.2
Restructuring Charges		1.4	3.0
Gain (Loss) on Disposition of Oil and Gas Property		(1.0)	(3.0)
Income before income taxes		$ 3.2	$ 76.0

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The designation of funds furnished by a borrower to a lender to assure future payments of the borrower's real estate taxes and insurance obligations with respect to a mortgaged property. Escrow deposits may be made for a variety of other purposes such as earnest money and contingent payments. This element excludes replacement reserves which are an escrow separately provided for within the US GAAP taxonomy.

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Amount of gain (loss) on sale or disposal of proven and unproven oil and gas properties.

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The net amount of other operating income and expenses, the components of which are not separately disclosed on the income statement, from items that are associated with the entity's normal revenue producing operations.

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The cash inflow to dispose of long-lived, physical assets and mineral interests in oil and gas properties used for normal oil and gas operations.

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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