Basis of Presentation ImpaIrment of Long Lived Assets (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($)
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Oil and Gas Properties	$ 404.4
Other impairment [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Oil and Gas Properties	1.6
Uinta Basin Divestiture [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Oil and Gas Properties	$ 402.8