Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) contract	Dec. 31, 2016 USD ($) mi	Dec. 31, 2015 USD ($)	May 31, 2017 USD ($)
Property, Plant and Equipment [Line Items]
Depreciation	$ 418,200,000	$ 386,900,000	$ 331,300,000
Property, plant and equipment, disposals	8,400,000	106,600,000
Expected proceeds from insurance settlements	6,100,000
Proceeds from sale of property	2,300,000	93,100,000	1,000,000
Loss on disposition of assets	0	(13,200,000)	(1,200,000)
Proceeds from insurance settlement	400,000	300,000	2,900,000
Impaired assets to be disposed of by method other than sale, carrying value of asset			5,100,000
Gain on business interruption insurance recovery			2,400,000
Provision for loss on contracts	$ 26,900,000	44,800,000
Number of contracts, specified delivery | contract	1
Accumulated other comprehensive loss	$ (2,000,000)	0		$ (2,200,000)
Allowance for doubtful accounts receivable	300,000	100,000
Environmental remediation expense	900,000	0	$ 3,500,000
Debt issuance costs, noncurrent, net	$ 26,200,000	$ 24,600,000
Sales Revenue, Net | Customer Concentration Risk | Net Devon Investment
Property, Plant and Equipment [Line Items]
Concentration risk	14.40%	18.50%	16.60%
Sales Revenue, Net | Customer Concentration Risk | Louisiana | Dow Hydrocarbons
Property, Plant and Equipment [Line Items]
Concentration risk	11.20%	10.80%	11.70%
Minimum
Property, Plant and Equipment [Line Items]
Intangible asset, useful life	10 years
Minimum | Accounting Standards Update 2014-09
Property, Plant and Equipment [Line Items]
Estimated decrease in revenue due to new accounting standard, percentage	6.00%
Maximum
Property, Plant and Equipment [Line Items]
Intangible asset, useful life	20 years
Maximum | Accounting Standards Update 2014-09
Property, Plant and Equipment [Line Items]
Estimated decrease in revenue due to new accounting standard, percentage	10.00%
EnLink Midstream Partners, LP
Property, Plant and Equipment [Line Items]
Gas balancing payable	$ 7,300,000	$ 7,100,000
Gas balancing receivable	5,800,000	3,900,000
Tangible asset impairment charges	$ 17,100,000		$ 12,100,000
North Texas Pipeline System
Property, Plant and Equipment [Line Items]
Proceeds from sale of property		84,600,000
Loss on disposition of assets		$ (13,400,000)
Number of miles of natural gas | mi		140
Customer One | Sales Revenue, Net | Customer Concentration Risk
Property, Plant and Equipment [Line Items]
Concentration risk	10.00%	10.00%	10.00%
Customer Two | Sales Revenue, Net | Customer Concentration Risk
Property, Plant and Equipment [Line Items]
Concentration risk	10.00%	10.00%	10.00%