Certain Balance Sheet Information (Intangible Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Less: accumulated amortization	$ 216.5	$ 191.6
Crestwood Equity Partners LP
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	43.5	53.7	$ 72.5
Intangible assets, Gross	770.3	788.8
Less: accumulated amortization	216.5	191.6
Total intangible assets, net	553.8	597.2
Crestwood Equity Partners LP | Customer accounts
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross	438.9	438.9
Less: accumulated amortization	112.1	89.8
Crestwood Equity Partners LP | Gathering systems and pipelines and related assets
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross	325.2	325.2
Less: accumulated amortization	100.8	82.0
Crestwood Equity Partners LP | Trademarks
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross	6.2	24.7
Less: accumulated amortization	3.6	19.8
CMLP
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	42.1	50.6	$ 69.3
Intangible assets, Gross	770.3	773.3
Less: accumulated amortization	216.5	177.6
Total intangible assets, net	553.8	595.7
CMLP | Customer accounts
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross	438.9	438.9
Less: accumulated amortization	112.1	89.8
CMLP | Gathering systems and pipelines and related assets
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross	325.2	325.2
CMLP | Acquired storage contracts
Finite-Lived Intangible Assets [Line Items]
Less: accumulated amortization	3.6	5.8
CMLP | Trademarks
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross	6.2	9.2
Less: accumulated amortization	$ 100.8	$ 82.0