Significant Accounting Policies - Narrative (Details)	1 Months Ended	3 Months Ended	12 Months Ended
	May 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) contract	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) mi	Jan. 01, 2019 USD ($)	May 31, 2017 USD ($)
Property, Plant and Equipment [Line Items]
Decrease in revenue from contract with customer			$ 7,693,800,000
Long-term purchase commitment, expected gross operating margin	$ 135,100,000
Long-term purchase commitment, deficiency fee received	19,700,000
Financing receivable, gross	$ 58,000,000
Financing receivable, interest rate, stated percentage	8.00%
Overriding royalty interest percentage	1.00%
Contract restructuring income		$ 45,500,000
Depreciation			453,800,000	$ 418,200,000	$ 386,900,000
Property, plant and equipment, disposals			2,100,000	8,400,000	106,600,000
Proceeds from sale of productive assets			1,700,000	2,300,000	93,100,000
Loss on disposition of assets			(400,000)	0	(13,200,000)
Expected proceeds from insurance settlements				6,100,000
Proceeds from sale of property			1,900,000	2,300,000	93,100,000
Proceeds from insurance settlement					300,000
Provision for loss on contracts			$ 9,000,000	26,900,000
Number of contracts, specified delivery | contract			1
Accumulated other comprehensive loss			$ (2,000,000)	(2,000,000)			$ (2,200,000)
Allowance for doubtful accounts receivable			300,000	300,000
Environmental remediation expense			0	0	0
Debt issuance costs, noncurrent, net			24,500,000	26,200,000
Louisiana
Property, Plant and Equipment [Line Items]
Tangible asset impairment charges			24,600,000
Crude and Condensate
Property, Plant and Equipment [Line Items]
Tangible asset impairment charges			$ 109,200,000
Minimum
Property, Plant and Equipment [Line Items]
Intangible asset, useful life			5 years
Maximum
Property, Plant and Equipment [Line Items]
Intangible asset, useful life			20 years
EnLink Midstream Partners, LP
Property, Plant and Equipment [Line Items]
Gas balancing payable			$ 12,400,000	7,300,000
Gas balancing receivable			10,400,000	5,800,000
Tangible asset impairment charges				$ 17,100,000
North Texas Pipeline System
Property, Plant and Equipment [Line Items]
Loss on disposition of assets					(13,400,000)
Proceeds from sale of property					$ 84,600,000
Number of miles of natural gas | mi					140
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Property, Plant and Equipment [Line Items]
Decrease in revenue from contract with customer			$ (671,000,000)
Percentage decrease in revenue from contract with customer			8.00%
Scenario, Forecast | Accounting Standards Update 2016-02
Property, Plant and Equipment [Line Items]
Right-of-use asset (less than)						$ 75,000,000
Lease liability (less than)						$ 75,000,000
Delaware Basin JV | NPG
Property, Plant and Equipment [Line Items]
Noncontrolling interest, ownership percentage by parent			49.90%
Ascension JV | Marathon Petroleum and Resources LLC
Property, Plant and Equipment [Line Items]
Noncontrolling interest, ownership percentage by parent			50.00%