Acquisitions & Divestitures Pro Forma (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenues	$ 390.1	$ 382.4	$ 1,193.9	$ 977.4
Net income (loss)	$ (3.3)	$ (50.9)	$ 119.0	$ (1,111.7)
Earnings Per Share, Basic	$ (0.01)	$ (0.21)	$ 0.49	$ (5.15)
Earnings Per Share, Diluted	$ (0.01)	$ (0.21)	$ 0.49	$ (5.15)
2016 Permian Basin Acquisition [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenues		$ 382.4		$ 977.4
Net income (loss)		$ (50.9)		$ (1,111.7)
Earnings Per Share, Basic		$ (0.21)		$ (5.15)
Earnings Per Share, Diluted		$ (0.21)		$ (5.15)
Pro Forma Revenue		$ 387.3		$ 991.9
Pro Forma Net Income (Loss)		$ (51.3)		$ (1,113.4)
Pro Forma Earnings Per Share, Basic		$ (0.21)		$ (5.16)
Pro Forma Earnings Per Share, Diluted		$ (0.21)		$ (5.16)

The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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