Other Long-term Liabilities, Contingent Consideration (Details) - USD ($)	3 Months Ended		9 Months Ended		11 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Mar. 01, 2017
Other Liabilities Noncurrent [Line Items]
Change in contingent considerations	$ 16,600,000	$ (126,800,000)	$ 12,100,000	$ (125,600,000)
Permian Acquisition [Member]
Other Liabilities Noncurrent [Line Items]
Preliminary acquisition date fair value of the contingent consideration	416,300,000	416,300,000	416,300,000	416,300,000		$ 416,300,000
Change in contingent considerations	16,600,000	$ (126,600,000)	12,000,000	$ (125,500,000)	$ (99,300,000)
Additional cash paid in potential earn-out payment					317,000,000
Permian Acquisition contingent consideration, estimated current portion	329,000,000		329,000,000		$ 6,800,000
Permian Acquisition [Member] | Accounts Payable and Accrued Liabilities [Member]
Other Liabilities Noncurrent [Line Items]
Fair value of first potential earn-out payment	0		0
Fair value of second potential earn-out payment	$ 329,000,000		$ 329,000,000