Significant Accounting Policies - Summary of Changes in Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contract with customer	$ 7,693.8
Product sales
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contract with customer	6,512.3	$ 4,358.4	$ 3,008.9
Product sales—related parties
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contract with customer	41.0	144.9	134.3
Midstream services
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contract with customer	763.3	552.3	467.2
Midstream services—related parties
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contract with customer	377.2	$ 688.2	$ 653.1
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contract with customer	(671.0)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 | Product sales
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contract with customer	(235.0)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 | Product sales—related parties
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contract with customer	(52.0)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 | Midstream services
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contract with customer	(357.0)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 | Midstream services—related parties
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contract with customer	$ (27.0)