Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Net Deferred Tax Liability, Decrease Due To Regulation	$ 1.3
Deferred:
Total deferred	2.1	$ 3.1	$ 3.6
(Provision) benefit for income taxes	0.8	(0.3)	1.4
Crestwood Equity Partners LP
Current:
Federal	(1.1)	(3.2)	(1.6)
State	(0.2)	(0.2)	(0.6)
Total current	(1.3)	(3.4)	(2.2)
Deferred:
Federal	2.1	3.0	2.9
State	0.0	0.1	0.7
Total deferred	2.1	3.1	3.6
(Provision) benefit for income taxes	0.8	(0.3)	1.4
Deferred tax asset:
Basis difference in stock of company	0.2	0.2
Total deferred tax asset	0.2	0.2
Deferred tax liability:
Basis difference in stock of acquired company	(3.5)	(5.5)
Deferred Tax Liabilities, Gross	(3.5)	(5.5)
Total deferred tax liability	(3.3)	(5.3)
CMLP
Current:
Federal	0.0	0.0	0.0
State	0.0	0.2	(0.3)
Total current	0.0	0.2	(0.3)
Deferred:
Federal	0.0	0.0	0.0
State	0.0	(0.2)	0.3
Total deferred	0.0	(0.2)	0.3
(Provision) benefit for income taxes	0.0	0.0	$ 0.0
Deferred tax asset:
Basis difference in stock of company	0.0	0.0
Total deferred tax asset	0.0	0.0
Deferred tax liability:
Basis difference in stock of acquired company	(0.7)	(0.7)
Deferred Tax Liabilities, Gross	(0.7)	(0.7)
Total deferred tax liability	$ (0.7)	$ (0.7)