Business Combinations, Purchase Price Allocation (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 29, 2018	Dec. 31, 2017
Liabilities assumed in business combination:
Goodwill	$ 5,745.2		$ 5,745.2
Delaware Basin Gas Processing LLC [Member]
Consideration:
Cash paid for remaining 50% equity interest in Delaware Processing	153.6
Fair value of our 50% equity interest in Delaware Processing held before the acquisition	146.4
Total consideration	300.0
Assets acquired in business combination:
Other current assets, including cash of $3.8 million		$ 12.7
Property, plant, and equipment		200.0
Total assets acquired		301.9
Liabilities assumed in business combination:
Current liabilities		(1.3)
Long-term liabilities		(0.6)
Total liabilities assumed		(1.9)
Total assets acquired less liabilities assumed		300.0
Total consideration given for ownership interests	$ 300.0
Goodwill		0.0
Description of Business Combination:
Cash acquired		3.8
Delaware Basin Gas Processing LLC [Member] | Customer relationship intangibles [Member]
Assets acquired in business combination:
Intangible assets		10.4
Delaware Basin Gas Processing LLC [Member] | Contract-based intangibles [Member]
Assets acquired in business combination:
Intangible assets		$ 78.8