Basis of Presentation and Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions				12 Months Ended
	Jan. 01, 2018	Jun. 21, 2017	Jun. 03, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary Of Significant Accounting Policies [Line Items]
Assets Held-for-sale, Not Part of Disposal Group				$ 3.0
Loss on long-lived assets, net				(65.6)	$ (65.6)	$ (821.2)
Inventory				68.4	66.0
Estimated Cost to Build				180.0
Contribution of Property		$ 69.0
Net proceeds from sale of assets				225.2	972.7	$ 2.7
Debt Issuance Costs, Net				28.4	34.0
Property, plant and equipment				2,285.2	2,555.4
Deferred revenue				$ 0.6	$ 7.5
Percentage of gross income from qualifying sources required to be subject to federal income tax, minimum				90.00%
Discount rate				12.00%	19.00%	15.00%
Increase (Decrease) in Intangible Assets, Current					$ 8.5
Goodwill impairment				$ 38.8	162.6	$ 1,406.3
Increase (Decrease) in Other Current Assets and Liabilities, Net					11.2
West Coast
Summary Of Significant Accounting Policies [Line Items]
Goodwill, Acquired During Period				2.4
Impaired assets to be disposed of				81.4
Fair value disclosure				66.4
Impairment of intangible assets				0.8
Goodwill impairment				2.4	0.0	85.9
Granite Wash
Summary Of Significant Accounting Policies [Line Items]
Impaired assets to be disposed of						8.5
Barnett
Summary Of Significant Accounting Policies [Line Items]
Impaired assets to be disposed of						354.4
Impairment of intangible assets						238.9
Goodwill impairment				0.0	0.0	257.2
Fayetteville
Summary Of Significant Accounting Policies [Line Items]
Impaired assets to be disposed of						61.9
Impairment of intangible assets						70.9
Goodwill impairment				0.0	0.0	72.5
Haynesville
Summary Of Significant Accounting Policies [Line Items]
Impaired assets to be disposed of						45.7
Impairment of intangible assets						6.0
Marcellus
Summary Of Significant Accounting Policies [Line Items]
Loss on long-lived assets, net				2.5
Goodwill impairment				0.0	8.6	0.0
Watkins Glen
Summary Of Significant Accounting Policies [Line Items]
Impaired assets to be disposed of						31.2
Trucking
Summary Of Significant Accounting Policies [Line Items]
Impairment of intangible assets					31.4
Goodwill impairment				0.0	29.5	148.4
Natural Gas Liquids
Summary Of Significant Accounting Policies [Line Items]
Inventory				67.9	56.7
CMLP
Summary Of Significant Accounting Policies [Line Items]
Loss on long-lived assets, net				(65.6)	(65.6)	(227.8)
Inventory				68.4	66.0
Net proceeds from sale of assets				225.2	972.7	2.7
Property, plant and equipment				2,615.3	2,885.5
Deferred revenue				0.6	7.5
Goodwill impairment				38.8	162.6	1,149.1
Goodwill, Impaired, Accumulated Impairment Loss				1,399.3
Crestwood Equity Partners LP
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment				2,285.2	2,555.4
Goodwill impairment				38.8	$ 162.6	1,406.3
Goodwill, Impaired, Accumulated Impairment Loss				$ 1,656.5
Jackalope Gas Gathering Services, LLC
Summary Of Significant Accounting Policies [Line Items]
Equity method investment, other than temporary impairment						51.4
Powder River Basin Industrial Complex, LLC
Summary Of Significant Accounting Policies [Line Items]
Equity method investment, other than temporary impairment						$ 23.4
Minimum
Summary Of Significant Accounting Policies [Line Items]
Discount rate				10.00%	10.00%	9.00%
Maximum
Summary Of Significant Accounting Policies [Line Items]
Discount rate				12.00%	19.00%	12.00%
Equity Method Investments [Member]
Summary Of Significant Accounting Policies [Line Items]
Discount rate						15.50%
Stagecoach Gas Services LLC
Summary Of Significant Accounting Policies [Line Items]
Net proceeds from sale of assets					$ 3.0
Equity method ownership percentage				50.00%
Property, Plant and Equipment, Gross, Period Increase (Decrease)					(1,127.6)
Stagecoach Gas Services LLC | CEGP
Summary Of Significant Accounting Policies [Line Items]
Net proceeds from sale of assets			$ 975.0		$ 975.0
Stagecoach Gas Services LLC | CMLP
Summary Of Significant Accounting Policies [Line Items]
Equity method ownership percentage			50.00%		50.00%
Subsequent Event
Summary Of Significant Accounting Policies [Line Items]
New Accounting Pronouncement Change in Balance Sheet Classification	$ 69.1
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 20.0