Certain Balance Sheet Information (Accrued Expenses and Other Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Apr. 30, 2019	Apr. 09, 2019	Apr. 08, 2019	Dec. 31, 2018
Accrued Expenses and Other Liabilities [Line Items]
Deferred revenue	$ 8.8				$ 12.0
Accrued expenses and other liabilities	161.7				112.4
CMLP
Accrued Expenses and Other Liabilities [Line Items]
Accrued expenses	60.3				63.7
Accrued property taxes	6.1				2.6
Income tax payable	0.3				0.3
Interest payable	25.6				19.8
Accrued additions to property, plant and equipment	38.0				10.5
Operating leases	18.1
Finance leases	3.2
Finance leases					2.4
Deferred revenue	8.8				12.0
Accrued expenses and other liabilities	160.4				111.3
Crestwood Equity Partners LP
Accrued Expenses and Other Liabilities [Line Items]
Accrued expenses	61.6				64.8
Accrued property taxes	6.1				2.6
Income tax payable	0.3				0.3
Interest payable	25.6				19.8
Accrued additions to property, plant and equipment	38.0				10.5
Operating leases	18.1
Finance leases	3.2
Finance leases					2.4
Deferred revenue	8.8				12.0
Accrued expenses and other liabilities	$ 161.7				$ 112.4
Jackalope Gas Gathering Services, LLC
Accrued Expenses and Other Liabilities [Line Items]
Equity method ownership percentage	0.00%	50.00%	50.00%	50.00%
Jackalope Gas Gathering Services, LLC
Accrued Expenses and Other Liabilities [Line Items]
Accrued expenses	$ 16.2