Financial Instruments (Details) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($) Bcf
Not Designated as Hedging Instrument \| Non-current asset
Derivatives, Fair Value [Line Items]
Derivative asset, gross	$ 0.7	$ 0.7
Not Designated as Hedging Instrument \| Current asset
Derivatives, Fair Value [Line Items]
Derivative asset, gross	3.2	3.2
Not Designated as Hedging Instrument \| Current liabilities
Derivatives, Fair Value [Line Items]
Derivative liability, gross	0.0	0.0
Not Designated as Hedging Instrument \| Non-current liability
Derivatives, Fair Value [Line Items]
Derivative liability, gross	0.3	$ 0.3
Commodity swaps
Derivatives, Fair Value [Line Items]
Hedged portions of expected sales of equity production \| Bcf		12.2
Commodity swaps \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Realized gain on derivatives	2.0	$ 2.5
Unrealized gain on derivatives	0.0	$ 3.5
Basis Swap
Derivatives, Fair Value [Line Items]
Hedged portions of expected sales of equity production \| Bcf		12.2
Level 2 \| Commodity swaps \| Not Designated as Hedging Instrument \| Prepaid and other current assets
Derivatives, Fair Value [Line Items]
Derivative assets (liabilities), net	3.2	$ 3.2
Level 2 \| Commodity swaps \| Not Designated as Hedging Instrument \| Non-current asset
Derivatives, Fair Value [Line Items]
Derivative assets (liabilities), net	$ (0.4)	$ (0.4)

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

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