The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Goodwill and Other Intangible Assets (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	May 31, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 03, 2018	Dec. 31, 2017
Goodwill [Line Items]
Goodwill		$ 796,359,000		$ 796,359,000			$ 0
Impairment of Other Intangible Assets		0	$ 0	18,650,000	$ 0
Amortization expense		$ 1,638,000	$ 0	$ 5,293,000	$ 0
Useful life, customer relationship intangible assets				17 years
Midstream Acquisition [Member]
Goodwill [Line Items]
Goodwill						$ 796,359,000
Other intangible assets						$ 128,781,000
Customer Relationships [Member] \| Midstream [Member]
Goodwill [Line Items]
Impairment of Other Intangible Assets	$ 18,650,000			$ 18,650,000