Certain Balance Sheet Information (Property, Plant And Equipment) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 2,598,100,000	$ 2,285,200,000
Less: accumulated depreciation and depletion	568,400,000	464,400,000
Property, plant and equipment, net	2,029,700,000	1,820,800,000
Depletion	0	700,000	$ 700,000
Interest Costs Capitalized	5,000,000	2,900,000	700,000
Capital Leases, Balance Sheet, Assets by Major Class, Net	9,700,000	2,100,000
Crestwood Equity Partners LP
Property, Plant and Equipment [Line Items]
Property, plant and equipment	2,598,100,000	2,285,200,000
Less: accumulated depreciation and depletion	568,400,000	464,400,000
Property, plant and equipment, net	2,029,700,000	1,820,800,000
Depreciation	123,600,000	135,900,000	154,800,000
Crestwood Equity Partners LP | Gathering systems and pipelines and related assets
Property, Plant and Equipment [Line Items]
Property, plant and equipment	758,600,000	678,000,000
Crestwood Equity Partners LP | Facilities and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment	1,230,700,000	1,141,400,000
Crestwood Equity Partners LP | Buildings, land, rights-of-way, storage rights and easements
Property, Plant and Equipment [Line Items]
Property, plant and equipment	331,700,000	319,100,000
Crestwood Equity Partners LP | Vehicles
Property, Plant and Equipment [Line Items]
Property, plant and equipment	17,900,000	37,300,000
Crestwood Equity Partners LP | Construction in process
Property, Plant and Equipment [Line Items]
Property, plant and equipment	230,800,000	87,500,000
Crestwood Equity Partners LP | Office furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment	28,400,000	21,900,000
CMLP
Property, Plant and Equipment [Line Items]
Property, plant and equipment	2,928,200,000	2,615,300,000
Less: accumulated depreciation and depletion	725,900,000	607,800,000
Property, plant and equipment, net	2,202,300,000	2,007,500,000
Depreciation	137,700,000	150,000,000	$ 168,900,000
CMLP | Gathering systems and pipelines and related assets
Property, Plant and Equipment [Line Items]
Property, plant and equipment	901,500,000	820,900,000
CMLP | Facilities and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment	1,415,900,000	1,326,500,000
CMLP | Buildings, land, rights-of-way, storage rights and easements
Property, Plant and Equipment [Line Items]
Property, plant and equipment	335,400,000	322,800,000
CMLP | Vehicles
Property, Plant and Equipment [Line Items]
Property, plant and equipment	16,100,000	35,500,000
CMLP | Construction in process
Property, Plant and Equipment [Line Items]
Property, plant and equipment	230,800,000	87,500,000
CMLP | Office furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 28,500,000	$ 22,100,000