Basis of Presentation and Summary of Significant Accounting Policies (Goodwill, by Reporting Unit) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Beginning Balance	$ 147.6
Goodwill Impairments during the Period	0.0	$ 38.8	$ 162.6
Goodwill, Transfers	0.0
Goodwill, Written off Related to Sale of Business Unit	(9.0)
Ending Balance	138.6	147.6
Goodwill, Other Increase (Decrease)	(9.0)	(12.6)
Marcellus
Goodwill [Roll Forward]
Beginning Balance	0.0	0.0
Goodwill Impairments during the Period		0.0	8.6
Ending Balance	0.0	0.0	0.0
Arrow
Goodwill [Roll Forward]
Beginning Balance	45.9	45.9
Goodwill Impairments during the Period		0.0	0.0
Ending Balance	45.9	45.9	45.9
COLT
Goodwill [Roll Forward]
Beginning Balance	0.0	0.0
Goodwill Impairments during the Period		0.0	44.9
Ending Balance		0.0	0.0
West Coast
Goodwill [Line Items]
Impairment of intangible assets		0.8
Goodwill [Roll Forward]
Beginning Balance	0.0	2.4
Goodwill Impairments during the Period		2.4	0.0
Ending Balance	0.0	0.0	2.4
NGL Marketing and Logistics
Goodwill [Roll Forward]
Goodwill, Transfers	101.7
Goodwill, Written off Related to Sale of Business Unit	(9.0)
Ending Balance	92.7
Supply and Logistics
Goodwill [Roll Forward]
Beginning Balance	101.7	101.7
Goodwill Impairments during the Period		0.0	65.5
Goodwill, Transfers	(101.7)
Ending Balance	0.0	101.7	101.7
Storage and Terminals
Goodwill [Roll Forward]
Beginning Balance	0.0	36.4
Goodwill Impairments during the Period		36.4	14.1
Ending Balance	0.0	0.0	36.4
US Salt
Goodwill [Roll Forward]
Beginning Balance	0.0	12.6
Goodwill Impairments during the Period		0.0	0.0
Goodwill, Written off Related to Sale of Business Unit		(12.6)
Ending Balance	0.0	0.0	12.6
Trucking
Goodwill [Line Items]
Impairment of intangible assets			31.4
Goodwill [Roll Forward]
Beginning Balance	0.0	0.0
Goodwill Impairments during the Period		0.0	29.5
Ending Balance	0.0	0.0	0.0
CMLP
Goodwill [Roll Forward]
Beginning Balance	147.6
Goodwill Impairments during the Period	0.0	38.8	162.6
Ending Balance	138.6	147.6
Crestwood Equity Partners LP
Goodwill [Roll Forward]
Beginning Balance	147.6	199.0
Goodwill Impairments during the Period		38.8	162.6
Ending Balance	138.6	147.6	199.0
Marketing Supply and Logistics
Goodwill [Roll Forward]
Beginning Balance	101.7
Goodwill Impairments during the Period		38.8	109.1
Ending Balance	92.7	101.7
Marketing Supply and Logistics \| CMLP
Goodwill [Roll Forward]
Beginning Balance	101.7
Goodwill Impairments during the Period		38.8	$ 109.1
Ending Balance	$ 92.7	$ 101.7

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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